I’ve run Proton without Steam for a few games. You’ve pretty much got the same code that Steam uses and most of their changes make it upstream eventually, so they’re not holding you hostage with being able to run your games. It just might get less convenient. There are other Linux game launchers that have good compatibility.

Steam and the company behind it have done wonders for Linux. They’ve given publishers a reason to care, they are providing strength and resources to fix bugs and libraries they care about, and generally have done very well in sharing their contributions with the community.

I do think this is a valid concern that we need to keep in mind, but I don’t think that we are at risk just yet. Valve is a business but as businesses go, they’re pretty cool.