I thought I’d record my experiences with this monitor, as I have recently purchased it and have had a few issues getting it to run.
Issue 1.
QHD wouldn’t work out of the box. I had to set up my xorg.conf for 50Hz for that resolution to be detected. I’m not using Wayland so I can’t comment on its behavior or even how to configure it. Here is my config setting.
The USB-C cable provided by Dell would not work either for the display or hub. I have to use HDMI for the display and a USB-C to USB-A cable plugged into my SS port to get the monitor’s hub to work.
Hope this is useful for anyone trying to get this monitor or one of its relatives to work.
I think that that is expected behavior i.e. USB-C is not supported on the Librem 13 (or Librem 15) for video output i.e. the so-called DisplayPort altmode of USB-C.
@kieran is correct about display over USB-C not being supported.
As for your first question, there have been posts on the forum about similar issues when it comes to detecting display modes and my UP2516D also requires me to introduce its native mode explicitly. Here is a link to what I think is the most related issue on the bug track.
Thanks for the advice but I wasn’t posting a question, just documenting my solution for others who may have a similar monitor. The important point is that I got QHD and the usb-hub working, albeit suboptimally.