https://bugs.winehq.org/show_bug.cgi?id=48006
--- Comment #26 from Andrew Church achurch+wine@achurch.org --- (In reply to a-1 from comment #25)
There is a description that says "Fix the new Final Fantasy XIV Online launcher."
https://github.com/ValveSoftware/Proton/releases/tag/proton-7.0-3
Good find, but it looks like those fixes have already been incorporated into vanilla Wine as well.
As a starting point, I've confirmed that applying all differences in jscript and mshtml from wine-8.17 to current Proton HEAD (8a8ec5f) allows the new launcher to work, at least to the extent of being able to log in:
for path in dlls/{jscript,mshtml}; do diff -urN {wine-8.17,proton-wine}/$path; done | (cd wine-8.17; patch -p1)
(I can't seem to press Enter from the OTP field to log in as I could do in the old launcher, but I've never actually used the new launcher on Windows, so I don't know if that's something missing in Wine or just a change in launcher behavior.)