The way that the Sync function is implemented is mostly alright: it reads KDE config files and writes entries to SDDM's config file.

However, there's two user files that are being copied: plasmarc, kdeglobals.

On top of that the user's whole fontconfig folder is also copied. (Not quite correctly though; the files in subdirs are not copied = font syncing cannot possibly work)

For security reasons it would be best not to do any file and folder copy operations.

PLAN:

1. using KConfig create new plasmarc and kdeglobals files for SDDM and write relevant settings into them
2. grab the fonts.conf XML content and copy it into SDDM's fonts.conf file
3. for now remove the (botched) support for syncing the font as D23257 and the patch SDDM 0.19 is going to come with will re-add this in a proper way

Dilemma: With the scope of changes planned, is this even viable for 5.18?