@jinliu, with org.kde.breeze.desktop, they still don’t look correct, but they look slightly better:
That would be kf6-breeze-icons-6.13.0-2.fc42.x86_64, although I’d have presumed it’d be the thumbnailer, not icon theme:
@RGB, that’s demonstrated that they’re solely corrupted below a certain size:
Reverting doesn’t remediate it. Perhaps, I need to clear the cache. IDK how to.