Avoid online tournaments with modded Switches. Nintendo’s telemetry can detect mismatched title versions if you use cheats. Stick to local wireless or LAN play.
Persona 4 Arena Ultimax (P4AU) remaster for Nintendo Switch is the most content-complete version of the game, though it notably lacks certain online features present on other platforms. Update Overview & Version Details Version 1.0.2 persona 4 arena ultimax switch nsp update hot