Your setup is fine. But add the USB Type-A to Type-C cable between the two to access the four USB Type-A downstream ports.

The U2520D has the following video IN ports = HDMI/DP (DisplayPort)/USB Type-C

This is to allow PC's with different video OUT ports to work on the U2520D. To access the U2520D three USB Type-A downstream ports, you must also connect to the PC either the USB Type-A to Type-C cable or the USB Type-C to C cable. Below are three possible configurations =

PC DP out port --> U2520D DP to DP cable --> U2520D DP in port
PC USB Type-A port --> U2520D USB Type-A to Type-C cable --> U2520D USB Type-C in port

PC HDMI out port --> HDMI to HDMI cable --> U2520D HDMI in port
PC USB Type-A port --> U2520D USB Type-A to Type-C cable --> U2520D USB Type-C in port

PC USB Type-C port --> U2520D USB Type-C to C cable --> U2520D USB Type-C in port

@mattwoeit  It would have helped if you had specified the laptop model you have.  But some laptops have USB-C ports, and in some cases those ports support the optional features of video output and/or system charging.  If you have a system with a USB-C port that supports all of those features, then you can use the USB-C to USB-C cable to connect your laptop to the display, and you will be able to send video to your display, receive power from your display, and exchange USB data in order to use the USB ports on the display as a hub for your system, all over that single cable.  The U2520D supports providing up to 90W of power, so as long as that's enough to run your system optimally, you've essentially got a docking station experience.

Executive summary: Thanks to you both for the info. Very good chance I’ll connect it to my laptop (or docking station) even though I don’t really understand the benefits. Sounds like there are no cons, so why not.

Question #1: If I connect the Type-C-to-Type-C cable to my laptop (or docking station), do I still need the DisplayPort cable?

Question #2: My laptop has three Type-C ports. Two are “Thunderbolt 3 with power delivery” and one is “USB 3.2 Gen 2 with DisplayPort.” I’m currently using one of the Thunderbolt ports to connect the power cable to power. I’m using the DisplayPort one to connect my docking station to the laptop. My docking station (D6000) has one Type-C port, which is not being used. So I’ve got a total of four places to stick the Type-C cable from the monitor. Which of those four would you recommend that I use?

To respond to both replies:

My laptop is an XPS 15 9500. It has Type-C ports. I’m also using a D6000 docking station.

Sorry, I’m not technically savvy, so some of the benefits mentioned go over my head:

“Send video to your display”: I don’t get it. I can already watch Youtube videos on the monitor. And if I double-click AVI, MOV, or MP4 files on my laptop’s C drive, they already display on the monitor. I don’t understand this benefit you speak of.

“Receive power from your display”: I don’t get it. Why do I want power from my monitor? All the objects in my office (laptop, docking station, printer, speakers) are already getting power.

“Exchange USB data”: Do you mean transfer data from a USB thumb drive to my laptop? I can just stick it in the docking station. Why would I insert it into a monitor?

Btw, Chris mentioned four Type-A ports on the U2520D. I see only three. One on the side and two on the back. The fourth one (on the side) is a Type-C.

@mattwoeit  Ok, so when you said in your initial post that you were connecting the display to your laptop with a DisplayPort cable, did you actually mean you were connecting the display to your docking station via DisplayPort?  As a general tip, when asking for technical assistance/insight, it helps to provide technical information, in this case the full picture of your setup.  That very often will result in more relevant and accurate answers, and possibly surface possible problems or improvements that you might not have been aware of -- as is the case here since you're using an XPS 15 9500 with a D6000.  I'll come back to that.

Anyway, if you have a docking station, then a USB-C connection to a display is less useful.  The idea of a USB-C display is to give you docking station type functionality -- power, video, USB data, sometimes even Ethernet, all running through a single cable to the display -- without having to buy an actual docking station.  But if you already have a docking station and you're currently connecting the display to the docking station rather than the laptop itself, then it would probably make more sense to keep the DisplayPort cable connection for video and then optionally add a USB cable connection between the dock and display if you want to use the USB ports built into the display. If not, then no need to bother.  But the D6000's USB-C port does not support video output, so you wouldn't be able to connect the display to the D6000 with a USB-C cable and have it work properly.

But if you ever wanted to ditch the D6000 -- which you may want to -- then since the XPS 15 supports video output and system charging on all of its USB-C ports, then no you would not need a separate DisplayPort cable for video.  Again, USB-C is capable of carrying power, video, and USB data all simultaneously and all over a single cable, as long as your laptop's USB-C port supports all of those things, which is the case here.  When I said "send video to your display", I didn't mean movies.  I just meant that you could send a video signal to your display that will allow it to display an image, and therefore would not need DisplayPort when using a USB-C to USB-C cable.

In terms of the benefit of receiving power from the display instead of the power adapter, that's simply to reduce the number of cables you'd have to connect and disconnect as you come and go from your desk with your laptop.  So rather than having to connect a power source, a video cable, and a USB cable all separately (and maybe an audio cable), and disconnect all of them when you want to leave, you just have a single USB-C cable to connect and disconnect, and that single cable carries everything.  The additional benefit of receiving power from the display is that it frees up your system's own power adapter, so you can park it somewhere else in your home that you might use your laptop frequently, or just keep it as a dedicated travel charger rather than having to unpack it and pack it back up every time you come and go from your desk where the display is.

In terms of exchanging USB data, yes I meant that you could connect a flash drive to a USB port on the display and have it be available to your PC.  Given that you have a docking station, which you didn't initially mention, I concede that it's less useful.  But again, one of the appeals of USB-C displays is that they are essentially displays with docking stations built in, so you don't have to buy a separate docking station in the first place in order to achieve this "single cable connectivity" convenience.

Ok, now back to the fact that you have a D6000 and an XPS 15 9500.  That's a decidedly non-optimal combination of equipment.  Whereas most docking stations tap into native GPU outputs available from the system, the D6000 instead relies on "indirect display" technology called DisplayLink -- not to be confused with DisplayPort.  That has several drawbacks that I've written about in the post marked as the answer in this thread, including being unable to use your system's NVIDIA GPU (if yours has it) for any displays connected through that dock.  On top of that, the D6000 only provides up to 65W of power, whereas the XPS 15 9500 is designed for either 90W (if it does NOT have an NVIDIA GPU) or 130W (if it does).  Since you've also got power connected separately, that's not an issue, but Dell has dock models that can supply up to 130W and tap into native GPU outputs, like the WD19S 180W and WD19TBS (only comes as 180W).  If you had one of those, then you'd only have to connect that single cable between your system and the dock to cover everything, i.e. power, video, and USB, and you wouldn't have any DisplayLink drawbacks.  Or if your system does NOT have an NVIDIA GPU, you may be able to simply cut the dock out of your setup by connecting straight to your display using a USB-C cable, since in that case the display's 90W power delivery max will be adequate for your system to run optimally.  Here again, you'll avoid DisplayLink drawbacks and receive adequate power to run your system from the display, meaning you've freed up your system's own power adapter, AND you'll still have access to USB ports on the display.

If on the other hand your XPS 15 has an NVIDIA GPU and is therefore designed for a 130W power source, then you could still cut out the D6000 to avoid the drawbacks of DisplayLink, and connect to the display via USB-C to USB-C cable for video and USB data, but you'd want to keep the system's own power adapter connected as well so that the system has a "full strength" power source available.

Massive and sincere thanks for all that info. Very helpful. Point taken about providing all relevant tech info up front. Will try to do so in the future.

To answer your question: Yes, I meant that the DisplayPort cable is connected to the docking station, not directly to the laptop. The laptop doesn't have a DisplayPort female.

If the D6000 is not appropriate with an XPS, then it seems erroneous/false/misleading/unfortunate that https://www.dell.com/en-us/shop/dell-laptops/new-xps-15-touch-laptop/spd/xps-15-9500-laptop/xn9500cto220s lists the D6000 as one of the “Dell Recommended Accessories for XPS Laptops.” See screenshot below. I relied on that recommendation to buy the D6000. Looks like that was a $200 mistake.

The video card for my XPS is NVIDIA GeForce GTX 1650 Ti 4GB GDDR6. So you’re saying that my new monitor is “unable to use” my new laptop’s video card because of the inappropriate docking station. So if it can’t use the NVIDIA card, what is it using instead? Based on your D6000-bad-for-gaming link, you would conclude that my current setup is acceptable for email and spreadsheets but unacceptable for games, right?

Just to confirm: It’s OK that I have the power cord attached (laptop to wall) AND have the D6000 cord attached. That “double” source of power isn’t harmful, right? It sounds like you’re saying that the D6000 is too weak and therefore using both is not only acceptable but necessary, right?

Screenshot:

@mattwoeit  Happy to help.  I certainly agree that the D6000 being "advertised" with the XPS 15 9500 is unfortunate.  If you have the NVIDIA GPU, then unless something has changed with DisplayLink software or Windows since I last checked into this, then the NVIDIA GPU will only be usable for accelerating graphics content being displayed on the built-in display, and it could also be used for non-display tasks, such a video encoding/transcoding, machine learning, and other "GPGPU" (General Purpose GPU) workloads of that nature.

I would say that the D6000 is fine as a typical everyday productivity solution, but games would definitely be a problem, because on top of the loss of the NVIDIA GPU, you'll have the additional performance and image quality penalties of DisplayLink's compression that exist even with systems that only have a single GPU.  You might even find that full screen video is a bit of an issue in terms of motion and/or compression artifacts, though this might depend on the resolution of your display and what else is going on with your system when trying to watch it.

Yes, it is absolutely fine to have the power source attached alongside the D6000, in fact Dell expressly recommends that solution in cases like this where the dock doesn't adequately power the system.  For example, Dell's Precision 7000 Series systems are designed for 180W-210W of power, and Dell's first generation of USB-C and TB3 docks could only supply 130W, so they specifically told users to run this setup to maintain proper performance.  (Newer models in that product line have dual USB-C/TB3 connectors, and Dell later introduced the WD19DC dock that plugs into both of those connectors to allow it to run 210W of total power.)  The same problem can exist when connecting to a USB-C display that might not supply enough power for the specific system you're using, and the same solution is recommended there as well.  The system controls the amount of power it draws from any attached source(s).  The power source can't "force" power into the system.

Thanks again.

Here’s a thought: Instead of spending another $200 on a better docking station, what if I spent $50 on a DisplayPort-to-USB-C adapter (like this bad boy: https://www.dell.com/en-us/member/shop/dell-adapter-usb-c-to-displayport/apd/470-acfc/pc-accessories) and simply plugged the monitor “directly” into the laptop, via that adapter?

So I’d continue using the D6000 for the printer, keyboard, etc., but I wouldn’t use it for the monitor. Would that make all my problems go away?

@mattwoeit  Yes that would work, although given that the U2520D has a native USB-C input, I'm not sure why you'd want a USB-C to DisplayPort cable.  And based on the list of peripherals you mentioned, and the fact that the display has built-in USB ports, AND the fact that the dock doesn't adequately power your XPS 15 anyway, at that point I sort of question the benefit of the dock at all.  I'd suggest this setup instead:

• Disconnect the D6000
• Use the USB-C cable that came with the U2520D to connect the USB-C input on the U2520D to the USB-C port on the XPS.  At that point you'll have both video and USB data (to enable the USB ports built into the display) running over that single cable, rather than just video as you would have if you got a USB-C to DP cable.  You'll also have 90W of power coming from the display, which is better than the 65W available from the D6000 but still not ideal for your XPS 15.
• Connect the XPS's 130W power adapter to the XPS directly.
• Disconnect the USB peripherals that are currently connected to the D6000 and instead connect them to the USB ports built into the U2520D.  Or if you need more USB ports and/or the additional connectivity offered on the D6000, then connect the D6000 itself to one of the USB ports on the U2520D, using the USB-A adapter on the end of the D6000 cable.  The dock will continue to work just as well when connected through the USB hub built into the U2520D, and that way you'll avoid having yet another cable to connect directly to the system.