I've set the proton method aside for now (although full of promise and dreams of the day playing faf on linux is a four-click process sum total).
I tried lutris and while lutris is no proton, it leaves very little to be desired in fact I think the configs used by either are identical as I cannot really tell the two apart performance-wise.
Lutris starts the game up without the erroneous setting of "PROTON_NO_ESYNC": "0", (where it should be 1) that proton has so there's less config involved.
the other big plus is that again this is just wine so it should communicate with JAVA_FAF just as it did with Python_FAF.
the issue I'm getting (I think) relates to the run param you had to change (or add to)
by default it says "%s"
but I get this error message : https://pastebin.com/D7Ftjzm9
and I recall being told by someone to change that (to what I donnot recall) and after that it ran fine.
can anybody recall what it was, or did anybody ever get the FAF client to work and pair with FA under linux?