I posted the SDDM problem and the fix.
System Settings SDDM Theme Crashes - Plasma 6.7.0
NOTE: Installing the old System Settings KCM fixes this issue.
sudo zypper in --oldpackage https://download-repositories.opensuse.org/history/20260616/tumbleweed/repo/oss/x86_64/sddm-kcm6-6.6.5-1.1.x86_64.rpm