What KVM are you using that supports dual displays and allows you to mix and match between HDMI and DisplayPort inputs? And what display OUTPUTS does your KVM provide, and what types of cables are you using to connect them to what kind of inputs on the displays? When asking technical questions like this, it helps to provide technical details, like the specific models of all equipment you’re using and exactly how everything is connected.

And for the other laptop that you said is working properly (again without identifying its model), it’s not clear from your post if it works properly using the exact same cable setup you’re attempting with the 7573 or whether you’re using a different setup on that side of the KVM. And for that matter, have you swapped the laptops to use opposite inputs on the KVM?

@b105 well actually, upon checking the product page of the Inspiron 7573 here (https://www.dell.com/en-us/shop/cty/pdp/spd/inspiron-15-7573-2-in-1-laptop), the USB-C port is described only as “USB 3.1 Type-C”. That wording typically means that the USB-C port is a data-only port and does not support video output or system charging. Those features are optional on a USB-C port (so is any data beyond USB 2.0, actually), and not all systems with USB-C ports implement support for those features. The device that you see getting connected and disconnected could just be the cable itself, since USB-C video cables are actually active devices that contain a chip to tell the system to switch its USB-C port to run in “DisplayPort Alt Mode”. On my Latitude 7480 that does support video over USB-C, for example, when I connect a USB-C to DP cable, I see the actual cable in Device Manager.

In theory it’s possible that the system does support video over USB-C even though the specs don’t mention it — I just discovered a case like this involving a Dell Chromebook, for example — but Dell is normally good about calling out support for video output on USB-C ports when it’s available.

TESmart 4 Dual Monitor KVM 2 Model HDK0402A1U.   Using HDMIs coming from laptops to KVM's hdmi inputs. (cables provided by tesmart).  Then purchased Warrky USBC to DisplayPort adapter cords from amazon(4k @60hz).  Connected those from laptops USBc ports into KVM displayport inputs.  So two video outputs needed from each laptop, one is hdmi to hdmi kvm input and other is usbc converted to dipslayport into diplay port kvm input.  I swapped out both laptops, other laptop is a Dell Latitude 5590.  That laptop displays properly on both screens.  They both are using the same types of connections and same style output and KVM inputs.  So the latitude works find either way using either set of cables and either laptop connection.  After swapping out cords it seems like the issue is the with 7573 itself.  When I go to display settings on my 7573 it shows 3 monitors for 3 seconds then 2 monitors as it autodetect the monitors. It keeps doing this repeatedly.  I keep both laptops closed.  I have tried driver updates bios updates/checks etc.  But my left side monitor does not wake up, KVM HDMI output for Monitor1.  The Monitors are both the same.  LG29WK50S. and they only accept HDMI input.  So the KVM has two monitor outputs using HDMI.  I have a hdmi cord going from the KVM to each of the monitors.  So again latitude works fine whether I connect it to laptop 1 cables to the kvm or laptop 2's cables.  It still displays on both screen correctly.  

Thinking I could try to avoid this issue by purchasing another connection from amazon.  Brands name is Pluggable USB 3.0 to displayort adapter.  This would avoid using the usbc on the 7573 and use the standard USB port. 

@b105  The Latitude 5590 definitely supports video output over USB-C, whereas your Inspiron might not given that it’s not explicitly mentioned in that system’s specs. If you can get temporary access to a display with a DisplayPort input, you could test your Inspiron using the USB-C to DP cable going directly to a display just to see if it might be some weird interoperability issue with the specific combination of that system and the KVM.

Otherwise, that Plugable adapter will work, but the way those adapters are able to send video over a regular USB port is by using “indirect display” technologies. Plugable’s adapters use DisplayLink (not to be confused with DisplayPort). The catch with indirect display technology is that it can introduce some drawbacks that might be relevant to your use case. I wrote about those in detail in the thread linked below, specifically the post marked as the answer. The original question there was about gaming, but the answer applies more broadly.

https://www.dell.com/community/Alienware/Docking-Station-D6000-Very-Bad-Video-performance-for-gaming/td-p/6193369

Hey @jphughan, thanks a million for your time helping me.  I finally figured out the issue.  Its actually the Intel UHD 620 Graphics card that is the problem.  I found another post online and it talked about changing the settings within the graphics interface software from intel.  I had messed with this before but had no luck.  I've posted link below.  But again when I messed with this interface previously and up until the fix the new monitor was only recognized for about 3 seconds and then would disappear.  The monitor would not turn on, it would only appear as a display within the Intel software interface and then disappear.  So what I had to do was change the settings for the quick amount of time that both displays were recognized and then finally both displays locked in place.  I had to change the Quantization range to full.  And once the Arrange Displays section consistently showed both displays I clicked on the Multiple Display section and the Select Display mode drop down section finally showed the ability to Extend Desktop, since both displays were now showing at the same time. Once I clicked Extended Desktop Display Mode the left monitor finally activated and both monitors showed the dual extended display as they should. Once I got the new display working it still had the previous issue of blacking out for a couple seconds and then showing the screen again.  (from the short period of time that it was working before)  This would happen every couple mins.  So as is discussed in the link below the next step was to manually configure the display settings for the newly recognized monitor because the Intel card recognizes the new monitor as a Television.  This next step fixes the sporadic blinking out black. It was doing this naming convention before within the Intel interface but I didn't catch that it was putting TV as part of the LG Ultrawide name.   So I had to configure the display setting to what it needs to be manually.  Which is 2560x1080 at 59hz and change the Timing Standard to CVT-RB.  This step is supposed to make the Intel card recognize the Monitor as a monitor and not a TV.  (even tho it still names it a Digital Television2 LGUltrawide instead of Digital Display LGUltrawide).      

What a relief, lots of time trying to figure this out.  But again thanks for your assistance!!

Hopefully this can help someone else in the future.

Link below also shows pics of the Intel interface. 

 https://superuser.com/questions/1164766/external-monitor-is-washed-out-with-intel-hd-graphics/1164801#1164801

@b105  WOW! I have no idea why getting everything working required that level of manual/custom configuration effort on your end, but I’m glad you got it resolved!

I'm having the same issue with my brand new Inspiron 7306 2n1 and a brand new Plugable DisplayLink UD6950-Z.    The monitors switch back and forth and the computer wont even support the other peripherals connected to the Plugable when only one monitor is connected directly to the PC.  What a pain.  i'll try your solution