Installed from kali-linux-2022.3-live-amd64.iso
I made the mistake of thinking that Debian/Kali can safely be upgraded with "apt upgrade". Clearly it can not! After reboot my external display looked like an old VGA monitor.
I have googled this a lot and all I find is feeble attempts to do this and that with X11 or Xrandr or other such blind endeavors to fix the symptoms. Nobody seems to know what the actual source of the problem is i.e. what actually broke.
Was it the upgraded linux-firmware or Grub or what? I'm pretty sure it was not the kernel because I tried booting with the old kernel and I still only get 1900x1080px on the secondary display.
Can someone wiser tell me what was broken? Maybe then I can fix it.
Update: I'm not using any 3rd party drivers and both displays are correctly identified.
Update: Only error I could find in Xorg log.
[47.317] Markers: (--) probed, (**) from config file, (==) default setting,
(++) from command line, (!!) notice, (II) informational,
(WW) warning, (EE) error, (NI) not implemented, (??) unknown.
[47.317] (==) Log file: "/var/log/Xorg.0.log", Time: Thu Sep 22 09:34:02 2022
[47.319] (==) Using system config directory "/usr/share/X11/xorg.conf.d"
[47.319] (==) No Layout section. Using the first Screen section.
[47.319] (==) No screen section available. Using defaults.
[47.319] (**) |-->Screen "Default Screen Section" (0)
[47.319] (**) | |-->Monitor "<default monitor>"
[47.320] (==) No monitor specified for screen "Default Screen Section". Using a default monitor configuration.
Update: I removed '/usr/share/X11/xorg.conf.d/10-radeon.conf' but it did nothing.
Update: By scaling the external 'AOC International' display x2 I can get what looks like very blurry 4K screen.