if you are experiencing a slow data connection using the ethernet port on the back of the monitor, change the usb-c prioritization to high data speed as seen in the picture below.  The high resolution setting is for HDR if you are going to view a 4K video or game that requires high resolution.  If you need HDR and high speed data, use the usb-c port on your computer with a usb-c to ethernet adapter and set the usb-c prioritiation in the monitor to High Resolution to get the best of both worlds.

Here is online U2723QE documentation page. User's Guide page 29 =

Locally, I pay monthly for up to 400 Mbps download speeds.  For the most part, I achieve these speeds all day with a wired connection directly to my XPS 15 (9510).  I personally own this monitor (Dell U2723QE) and for whatever reason I am consistently seeing a 200-300 Mbps drop with a wired connection directly to the U2723QE (max speeds near 80 Mbps).  Not sure why this is, but this has been consistent for months even after updating firmware, drivers, etc.  Quite disappointing, but I'm sure there is room for error on my part here somewhere - although I don't know where.  Just wanted to get this out there as an FYI for anyone looking at this beautiful display.

I get full gigabit speed with a 2018 MacBook Pro. It sounds like you are only getting USB 2.0 speeds through your cable, Jumbiesaus. That may be because your laptop doesn't supply DP 1.4 - I couldn't confirm what revision it has from Dell's specs.