This is a continuation of Can't start a new Collab Deck , which was auto-closed. There Andrew had asked me:
@jakub.f , is it right that the Qt6 incompatible issues are only present in the latest Anki version? Did you try the Qt6 build for Anki version 2.1.64, @stephenmaturin ?
I just now downloaded and tried the Qt6 build for 2.1.64, and it failed in the same way.