as described in a previous post, I had some problems with a suddenly changing font in den SDDM login screen after installing additional fonts via System Control Center (in my case: Arial).
Maybe it’s of interest for someone else, therefore the solution:
Go to YAST -> Fonts -> Preferred Families and select “sans-serif”. Add the font “Noto Sans” into the list as the topmost/single entry. After this, SDDM will again use this font for showing the written parts in the login screen with theme Breeze. The configuration is stored in /etc/sysconfig/fonts-config