When I tried installing the Misery mod under linux I had quite some problems, as no specific guide was there to do it on steam.
I hope this guide will help other people that are struggling as I do.
The mod works flawlessly under linux, except some sudden crashes; but that's just stalker!

Download the Misery mod and extract the archive.
Open the terminal and go into that folder.
Find your steam library folder; by default that is /home/user/.steam/ where user is your username
Write this command in the terminal:
where x.yy is your Proton version.
Run the command and the installation process will begin.
At the end of the installation the mod is ready and you can start the game from steam.
P.S. Close steam during the installation, it could cause problems.