I used the following commands to get it to run (Big Sur 11.6.4 on a iMac 5k Late 2015)
1. sudo chmod -R 755 <PATH TO GAME.APP>
2. sudo xattr -dr com.apple.quarantine <PATH TO GAME.APP>
3. sudo chmod 777 <PATH TO GAME.APP>
4. sudo spctl --master-disable
IMPORTANT: If you're done playing the game you should enable Step 4 again, as it disables Apple Gatekeeper.
After that I also got the text issues at the start screen, but once I started a new game (First Menu Point) everything worked fine from there on.