SDDM theme fails to load

SDDM theme on my Bazzite laptop recently started failing to load, with the following error message:

The current theme cannot be loaded due to the errors below, please select another theme.

file:///usr/share/themes/01-breeze-fedora/Main.qml:214:25: Cannot assign to non-existent property “fontSize”

This is a new behavior, with no recent system changes made by me. Problem started before upgrading to 41, and persists post-upgrade.

There was an API change but the Breeze theme wasn’t updated to accomodate it. A workaround is to create a custom version of the SDDM Breeze theme, fixing this bug in the Main.qml file. There is a tutorial here that covers it Customizing a SDDM theme | CodinGarret.dev