KDE not recognizing monitors when multiple are plugged in

THis is an issue I’ve noticed while booting with the Live USB, and also using my installed OS. When I have two monitors connected to my laptop, both monitors have “No Output”, but are recognizing a cable. Let me first describe my setup.

I have an HP Envy x360 Laptop, which is connected to a Dell USB-C Thunderbolt Docking Station. Two monitors are connected to this docking station, using HDMI and Mini-Displayport. I have also tried connecting one of the monitors directly to my laptop’s HDMI port (and the other one connected via Mini-DP to the docking station) and there is no difference.

The issue is this: When I have all 3 displays connected (my laptop’s display, and both monitors), my laptop’s display works perfectly, and is the only recognized display (as shown in display settings and the window overview). However, when using xrandr, I can clearly see 3 displays: eDP (my laptop display), DisplayPort-3 (my HDMI monitor), and DisplayPort-4 (my Mini-DP monitor). I see the + icon set to the correct resolution (1920x1080) on both monitors, but no * (no chosen output mode). The eDP device correctly has a *. Currently, my only solution is to manually set the modes of both monitors, and specify their position in terms of coordinates or --right-of. This successfully allows me to “extend” my display, but as these displays are not recognized by Manjaro, I don’t see widgets and desktop icons for any of my monitors.

The most peculiar part of this, however, is that when unplugging my Mini-DP monitor, display signal is restored to the HDMI monitor, and the widgets show up correctly for that monitor, as if it was my “second” display. This does not happen when unplugging the HDMI monitor, though, and the Mini-DP monitor is still left with no Video Signal. And of course, when both monitors are unplugged from the docking station, the laptop display works perfectly.

I have successfully gotten xrandr's configuration to work (although it doesn’t save after a restart), and all monitors are definitely working at the same time. Is there some specific driver I’m missing? This is really a hassle, and I hope to get it fixed.

Just to clarify, if you open system settings and go to the monitor section you can’t see your monitors? It’s strange you can see them with xrandr but not in system settings.

Yep - that is correct. Adding on, here is some more strange behavior I have noticed:

On boot (when powering on the PC), the two monitors are connected as DisplayPort-1 and DisplayPort-2, which both show up on the system settings (my widgets and everything else work fine). However, when unplugging or plugging back in my docking station (or just the display cables individually), they get re-assigned to 4 and 5, and this bugs them out (they don’t show up in system settings, and I have to configure them via xrandr and autorandr).