If I use Simplified Chinese in Properties, EAC says "Failed to load the embedded resources." and it is failed to launch. Setting game language to English in Properties or launching game with EAC disabled can workaround this. I can still change game language in game ui if I set game language to English in Properties. As for the game failed to start even EAC problem is workarounded, that's because msvcp140.dll failed to load, you can run game with PROTON_LOG=1 to find it out. Following https://github.com/Winetricks/winetricks/pull/2345 to extract a correct msvcp140.dll and replace the broken one in system32 can launch the game and play. No need to downgrade Proton to 7.0, I use Proton GE 9.27 in the whole time. After those problems workarounded, game should launch with EAC enabled. Halo Reach Campain works fine, but I do not test other DLCs, nor Multiplay.