Well, that’s because Stage Manager support for external display has been pulled by Apple… but should arrive later this year.I just noticed this myself when testing iPadOS 16.1 RC on my wife's iPad Pro. Makes the whole stage manager rather useless for our use case to be honest. In the early iPadOS 16 BETA it would use the entire display so when connecting using USB-C (DisplayPort) to DisplayPort on our 3440x1440@175Hz we could get the full 3440x1440, 175Hz and HDR going. Now it's just a 3:2 mirror at 60Hz.
Yes. This is official news from Apple that monitor support is coming in later software update. As of this time, there is no official date. I would expect it to release next monthJust updated to iPad OS 16.1. I like Stage Manager. When are we going to get the external monitor support (extended screen mode)? I read somewhere that Apple would put it back to iPad OS for M1/M2 users later this year. Is this promised by Apple or just rumors?