
You can verify you have dumped a supported copy of the game by using the SHA-1 File Checksum Online at https://www.romhacking.net/hash/.
It’s so sad that Windows still doesn’t ship with an easy-to-use hash toolkit

Usually graphics are a one-way street, you can run all the game logic headless and then punt data over to graphics and forget it since the rendering doesn’t affect gameplay
I think that’s how the PS4 version of Shadow of the Colossus worked, they recompiled the PS2 code and just replaced the graphics layer with a newer graphics engine
BTW I couldn’t get AC5 full speed on Steam Deck so if anyone knows the right config hmu