Custom background or logo not working on Arch Linux when selecting from non-home folder

[blehz.]

ISSUE
When setting a custom background or custom logo on a non-steam game, after selecting the file, it doesn't do anything. Neither it shows up after the save and it's not in the shortcuts.vdf file. Setting a custom icon works.
This appears to happen when selecting a file from e.g. /games folder on the root system drive.
Selecting from the user home folder works.

Also tried the Beta but this doesn't even open the file dialog after trying it the first time.

OS
Arch Linux (multilib steam package), KDE Plasma, using xdg-desktop-portal-kde file dialog.

STEPS
Add Non-Steam game.
Select game in library.
Right click on title to set custom background or custom logo.
Choose a file (png or jpg).

EXPECTED
Custom background or custom logo is NOT set. Nothing changed.


Note:
This used to work a few months ago on Endeavour OS (Arch based, same package).