I’ve got Plugable UD-CAM dock and it works perfectly fine with my Dell Latitude 7480 laptop and USB, Ethernet and WQHD (2560 x 1440) Dell monitor.
Pretty much the same is applicable to my Samsung Galaxy S9 with only 1 exception - HDMI resolutions above FullHD (i.e. 1920x1080) are grayed-out in Dex settings (see attached screenshot).
Now given laptop works with the same monitor in its native WQHD resolution through the same dock all the hardware is in place, it is just some either incompatibility or misbehavior of the Samsung device I guess. What’s more if on the phone I switch from DeX to screen replication mode then real WQHD resolution is used - so again it seems to be some intentional limitation of DeX mode.
And my question would be if there’s something could be done to get higher resolutions of DeX working with non-Samsung docks as otherwise FullHD on 27 inch screen both looks blurry and doesn’t allow to use the screen estate efficiently.