Arma 3 doesn't work anymore

[panzergrenadier3 39]

Hello,

 

yestern day evening I was playing Arma 3 last time on my Linux PC. After that, there were no changes or updates on any programs except an update for Arma 3 via Steam. I've played with Proton 7 and with the original launcher, not the Unix-launche (because the unix launcher doesn't support battleye and it's not possible to play in multiplayer).

 

Today I've startet Arma 3 and get this error message:  Unexpected error occured: Specified cast is not valid. Details are stored in a text file on your desktop.

 

I cannot find the "desktop" folder and the file is not on my Linux desktop.

 

I've bought the game in 2017 and played on Windows the first years. Now I've got a Linux distro (Linux Mint 20.2) and played on this the last few weeks.

 

Is there any solution for this?