https://bugs.winehq.org/show_bug.cgi?id=52797
--- Comment #2 from Lars Loe madbyte@tuta.io --- sorry, I'm not really able to interpret the wine source code, but I guess what you mean is that the code I linked in wine.git already fixes the issue?
I've just searched for the UserDefinedAnnotation methods in latest Proton and they indeed are missing, so I assume the fixes just need to be pulled into a future Proton release?
If so, this can be closed.