Resolution of login screen to low

[AllesMeins]

I just did a fresh install of Kubuntu 20.04 on my system and I'm having problems with the initial login screen which is displayed at a very low resolution (looks like 800x600 or something like this). After I've inserted my password it switches to the right resolution but not before messing up my desktop (all widgets are moved into the upper right quarter of the screen, probably because of the low resolution of the login screen).

I didn' had this problem with my last installation on this machine when I was still using Ubuntu with Gnome and KDE in parallel. Can somebody help me how to fix this?

I'm using Kubuntu 20.04 with an Radeon HD 6670/7670 connected via DVI-D to my screen (2560x1440 native resolution)

[claydoh]

First try checking SDDM's settings to see if you have a Sync or 'sync settings' option, this may help here if the option is present (can\t recall if it is in 20.04)
If not, you may try enabling hidpi support via config edits:
https://wiki.archlinux.org/index.php/SDDM#DPI_settings

[AllesMeins]

Thank you for your reply - unfortunately both tips didn't bring any change. I've tried the sync-function and created the HiDPI-Config file and the resolution is still the same

[AllesMeins]

Okay, I fixed it! For anybody who might stumble upon this (and probably for myself looking again for the solution in 2 years :-) ): The problem in my case was that the system for some reason detected a "phantom monitor" with low resolution that was supposed to be connected. You can check for this via

[FONT=monospace][COLOR=#000000]Section "Monitor" [/COLOR]
       Identifier "VGA-0" 
       Option "Ignore" "1" 
EndSectionxrandr | grep ' connected' For me it showed my main monitor and also an "VGA-0 connected" with an resolution of 800x600. I guess because of this sddm took the safe road and switched down to the lowest resolution. I fixed it by telling XOrg to ignore this monitor. Add 

to [/FONT]/usr/share/X11/xorg.conf.d/10-radeon.conf