Isn`t your party mic binded on this key. If yes it may be because of the same reason as i had. There is post about it(https://forums.playdeadlock.com/threads/cant-join-party-on-linux.122533/post-231759) i think it is because of game freezes when you try to use party voice chat on linux
I found solution, i`ve already described it under another post so i just will leave link(https://forums.playdeadlock.com/threads/cant-join-party-on-linux.122533/post-231759)
UPDATE: While i was looking for reports with similar problems i saw this post(https://forums.playdeadlock.com/threads/linux-steam-game-crashes-when-using-text-chat-while-in-a-party.121535/). The guy had same problem but when he just unbinded party voice key the problem disappeared. The only...
Bro, thank you very much, i and my friend were suffering from this for 3 days and finally we can play together.(1 difference is that i had 'always active party mic' setting turned on but when i turned it of it worked)
I am on proton Experimental, but i also tried almost every other proton version that i can use, including version for cachy os and i still couldnt join party. What about steam version, i am using the newest version for arch.