@jeffgerstmann It seems like you tried VF5 during a short window when EAC was As Bad As Possible.
EAC worked fine, faster than Windows, then they updated to 1.08, and it stopped working for all Linux users, including Steam Deck.
Then on 02/03 they fixed it remotely; no Steam updates, no system updates, no word from Sega on what they changed.
Community assumption is that 1.08 included a new EAC client module version, and they needed to change the EAC server to match. https://steamcommunity.com/app/3112260/discussions/0/724650931393833549/