Yes it is a bug, achievements for this game don't work anymore on Linux.

Ok, thanx for the reply. Maybe some day that will be fixed. Atleast the game runs fine :)
As far as I know, Steam doesn't have an option at least yet to use windows version if a linux version exists. Banner Saga had a broken version for linux for a long time, the linux dev left the team and eventually they just removed the linux version completely since people couldn't play at all.

You could also try to install an older version of the game (the one from May 2015 should work):
https://www.reddit.com/r/Steam/comments/611h5e/guide_how_to_download_older_versions_of_a_game_on/

Originally posted by SapeChi:

Ok, thanx for the reply. Maybe some day that will be fixed. Atleast the game runs fine :)
As far as I know, Steam doesn't have an option at least yet to use windows version if a linux version exists. Banner Saga had a broken version for linux for a long time, the linux dev left the team and eventually they just removed the linux version completely since people couldn't play at all.

Steam let you install the Windows version even if a Linux version (native one) exists for the game you try to install.

You just have to FORCE using PROTON for ALL games (from your Steam Client Settings).
(in this case, EVEN games that haven't native Linux version, can be emulated with Proton valve WINE custom version).

Also, the achivement bug impact me aswell, I play also on Manjaro Linux.
Anyway, it's possible to install the WINDOWS version for me..
But it change nothing.

The old game version from 2015 seems the answer to trigger and unlock achievements.

Originally posted by Spacelotus:

Achievements works on linux now !

Kubuntu LTS 18.04

Finally?
Will try it later.

EDIT: I'm ok, after playing like what 2 seconds, I got a Steam Achievement yeah! ;)