I'm glad you got it going... But I'm even more excited of the news that TWRP is now functioning well enough to flash a ROM, even if it is just stock OOS. Can you root it (Magisk) as well with TWRP?It failed after what appeared to be a disconnect and reconnect, but I didnt have the driver installed for the device.
I was eventually able to recover, but the only thing that would work was the OnePlus 9 Pro India MSM tool. I have a OnePlus 9 Global (not pro, not India). So now Im trying to figure out how to get back to the proper image.
Update: After getting booted into the OP9 Pro India image, I was then able to get booted into TWRP and flash the correct full OTA zip for my device. I think Im on the right track now.
I've provided an AFH mirror for OOS' full OTA 220.127.116.11AA for convenient download.