Document Revision 1.2 [07/15/22]
Author Notes: Thanks to everyone who has been testing or using this installation process. I've refined the instructions to try to make this installation as simple and cross platform as humanly possible. I've also updated the Steam Deck instructions now that I have had mine for a while and thoroughly tested the installation process.
Final Fantasy IX should be installed like any standard steam game through the steam client. Ragarding compatibility layers: it should work with a stable release of Proton 7 (7.0.X recommended) through the steam client. This also includes controller support if you are using Steam's native controller configurations. If you have any problems with a given Proton release, I would also recommend trying the latest GloriousEggroll proton builds to se