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Alright, finally some clues.
1. The stuttering is caused by the game Launcher! NOT the game. When the launcher is closed after the game has started, there's no stuttering.
The real question is why and what is causing this. The moment launcher is closed, GPU is noticeably quieter.
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Launchers often have an actual browser in them and emulating all of the shit browsers do via vulkan can have a tendency to lead to this. E.g. you couldn't sanely use dxvk with the battle.net launcher for the longest time.
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Yeah could be, as the launcher broadcasts the news about the game. But the same launcher didn't cause any problems before. I'm not aware if the launcher was updated in the meantime.
One thing I noticed, it doesn't need to be closed - minimizing also works. It just cannot be present on the screen, even not behind the apps or other windows.
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Have you tried old Proton versions? Steam uses the experimental branch by default so it changes all the time; I've had games stop working after a Proton version change.
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Makes sense, a minimize normally unmaps the window completely so it's not rendering stuff anymore.
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Since the latest Mesa update 23.3.4 Launcher now works nicely too, as before.
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