To ensure games run well on Linux either via Native Linux builds or Windows games with Proton, part of the magic is in the Steam Linux Runtime. A new version of it, the Steam Linux Runtime 4.0 was recently put up with some pretty big changes.
What’s the point of it? It ensures Steam and games run through Steam on Linux work properly across all the many different Linux distributions. Another secret Valve sauce for Linux. Well, not secret at all but you get my meaning I’m sure.


You’re not alone. I had the same thing on two machines yesterday. (Not flatpack)
yeah, many people had that problem. it happened around the same time the Arc Raiders servers went offline. a buddy of mine couldn’t launch Steam, and when he did, it wouldn’t load his friends list. my theory is that the 350,000 people who were all reloading Steam and Arc Raiders over and over DDoSed the two services.
A decent error message would have been useful.
I don’t know if there’s an existing error message for “please stop reloading Steam all at once, the game will come back online just give them time”.