Just FYI I couldn’t get it working in endeavour os with different versions of proton.
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Check out this page of the Arch wiki: https://wiki.archlinux.org/title/Downgrading_packages. The downgrade script in the last section works great. Endeavour OS is Arch-based and uses the same package manager, so it should work. This works only with packages from the official repositories, for AUR packages, you need to downgrade manually.
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