I did some more patches and kept the build clean.
Also sent some existing fixes towards SLFO, so that they can still reach Leap 16.0 and later 16.1

Finally found the problem with cosmic-related packages. It was from cargo-i18n / i18n-embed-fl that already had a fix, that is still missing in our vendor.tar.

Additionally I did another test of the games repo and submitted fixes for 4 of the 9 issues found.

If we keep improving at this pace, we could be done in 2029.

That was what I thought mid-November.
And then something happened in ghc that fixed a lot of packages at the same time.
And https://qt-project.atlassian.net/browse/QTBUG-137440 also saw some movement, though we already applied workarounds to evade that problem.