https://bugs.winehq.org/show_bug.cgi?id=48006
--- Comment #35 from Andrew Church achurch+wine@achurch.org --- I've added a new PoC branch based on Wine 9.x: https://gitlab.winehq.org/achurch/wine/-/tree/ff14-launcher-9.x
The head of that branch is the first working commit found by git bisect on Proton's 9.0 branch, which was the same "first good" change I found on 8.x, and everything else is other commits needed to get that one to apply and build cleanly - 26 changes in total. I'm able to successfully log in and start the game client using these changes (plus the hide-wine-exports patch from staging to deal with the Windows vs Mac license issue).