Hello All,
I had a hard time updating to 12.1.
First, I tried OTA update, which failed miserably, leaving the system unbootable with the Install Monterey partition. My only option was to create a USB installer and try it again.
I then boot Big Sur 11.6.1 from my Lacie Thunderbolt SSD. Updated Big Sur to 11.6.2, had the BootRom updated and only then I created the USB installer for Monterey. After the creation of the USB Installer, I tried the installation several times without any success.
I was planning to get rid of the partition with Monterey and start from an empty SSD, but this morning I decided to give the USB Installer another try. This time I mounted the EFI partition and removed the APPLE folder with the 11,2 firmware and monitored the installation during every minute also pressing OPT after every reboot to make sure the correct option would be selected. After three reboots, I am back to Monterey 12.1.
Anyways, I hope the update goes smoothly for everybody.