8BitF0x

I don't see the Steam Deck buttons in the main menu UI, what does it look like?

I used ProtonUp-Qt to get Proton TKG.

Yup! I got a video demonstration posted here: https://youtu.be/22Rn03u1zPI

Alright, I gave it a go and it worked on my side. I was able to play a full match on Steam with no EAC errors using Proton TKG.