>>546212024
Apparently achievements don't work in the Linux version because it doesn't load some Steam API shit properly. (One of the ProtonDB reports also mentions this.) But it's fixable according to this Steam forum post.
This dude should just put a more concise list of steps on PC Gaming Wiki. What a shame that we're still posting fixes on forums in $(date +%Y). Did PCGW ever make a dent in this problem? Because that was the whole point of it. And it's still there, even though it's not very active, and frankly seems abandoned sometimes.