3 days after, I found the solution, thanks to a french Ubuntu wiki: https://doc.ubuntu-fr.org/steam
For recent Ubuntu versions, you have to launch steam with the environment variable LC_ALL set to C:
LC_ALL=C steam
Just put this line in a sh script in your ~/bin folder , which you'll use to launch steam as long as this particular issue is not solved.
I hope this'll help someone ;)
Nothing extracted yet.
I installed Steam for Linux for the first time, and got this issue with both Ubuntu's version and the one downloaded from Steam's website.
This is what I get when running Valve's version via a terminal:
Any ideas? Thanks in advance