For quite some time now Linux gamers have been reporting issues with lag spikes in various games on Steam when the Steam Overlay is disabled. It seems Valve may have finally found the cause and a fix is hopefully on the way.
There's been a bug report open on the Steam GitHub page since November 2024, with hundreds of comments discussing the issue. One workaround has been to set this as a launch option for games:
LD_PRELOAD="" %command%
However, that's only good if you know that workaround exists. Ideally, games should perform the same if you have the Steam Overlay enabled or disabled.
Writing on the GitHub, Valve contractor Timothee "TTimo" Besset wrote on May 19th:
Hey all - thanks for the reports. We believe we have a fix for this issue, it hasn't made it's way through our release pipeline yet but I'll update here when we do.
Hopefully then we'll see this problem solved soon.
Article taken from GamingOnLinux.com.
You can also find comments for this article on social media: 
hvcr 3 hours ago
It was this effen problem that was messing mount and blade warband for me, I had no idea, I tried so many things, all possible proton versions, all possible ingame configurations, I even convinced myself the problem was me using Z-ram, and so went through a lengthy process to disable it and start using a page-file again, nothing worked
I was sure it was a problem with my setup, it would have never occurred to me that the problem was that the effen overlay was DISABLED.... that makes 0 sense to me, having problems with it enabled? yeah, perfect sense, but DISABLED?! wtf?
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