I set modified EDID in GRUB. I have only 1 display.

I added new refresh rate for testing, but after enabling it I just get black screen. How to fix this issue?

SDDM main process is running as root and ignores all policies. So only way is modifying SDDM source code(

In this guide author dumped edid from disaplay and then loaded it without any modifications. So after reloading edid you can choose any resolution? Or I understood something wrong?

Thank you, it works! But I got weird behavior:

1. User sddm also cannot execute poweroff (it is ok) but if I press shutdown button in sddm it will poweroff (not ok).
2. If I press shut down in KDE Plasma I will get black screen and no sddm (I can restart it with systemctl restart sddm from tty and it will work again) How can I fix this bugs?

I think this is for applications not for graphical server

They all operates some way through systemd, so if operation is disabled via policy you cannot bypass it.

sasha@fedora:~$ /sbin/halt
Call to Halt failed: Interactive authentication required.