Okay. I am not an expert. This was just a suspect.
As a workaround I could imagine to make a script to configure the screens to a correct setting and put that script somewhere so that it gets executed at startup or login or so. arandr is your friend in generating such a script, if you don’t want to do it manually.
Otherwise you have to wait if some expert makes a statement. I am not really Linus Torvalds you know. I am just his forgotten twin. ^^
As this does happen with my Librem 14 on PureOS as well and connecting a display via HDMI doesn’t work too, the purism support currently thinks this is a hardware issue.