https://www.youtube.com/watch?v=ovOx4_8ajZ8&t=2746
I'm not sure I quite understand the issue Steve has with things updating when adding new cards.
Sure, updates during a single benchmark series is a problem but what is the issue with the system being updated for the next benchmarks?
Proton/amdgpu/Mesa receiving updates is no different than installing newer "Game Ready" drivers when a new GPU comes out.
I assume they don't go out of their way to install older (potentially incompatible) drivers on Windows just so they can compare two separate benchmarks.
Besides that, after disabling Flatpak and rpm-ostree updates in Bazzite, the only remaining variable is Proton. Which should be easily fixed by manually copying a fixed Proton version to their compatibility tools and using that.
