I recently installed the macOS Monterey beta on my personal laptop. It was horrible. Tabbing to and from Chrome would result in seconds of lag & beachball showing up. Sometimes Chrome would stop responding completely. I wanted to downgrade.
I couldn't do it via ordinary means. I couldn't just boot into the RecoveryOS because it was prompting me to reinstall Monterey. I didn't want that.
I know! I'll wipe the SSD...
Nah, macOS somehow keeps hold of the last version you've installed. I tried this a few times, with a few arcane keyboard shortcuts for good measure, but nothing worked.
The one thing that did work? Apple Configurator 2 running on another macOS computer that is NOT on the beta. Hence the rich part (I am not actually rich I have 3 MacBook Pro's - 2 of them are from work).
So here is what you do;
- Turn off the Monterey MacBook.
- Using a USB-C cable put one end in the leftmost USB-C port on the Monterey MacBook but it needs to be closest to the LCD. On my 13 inch it was the furtest port from me on the left hand side. It needs to be in this specific port.
- Put the other end in the 2nd MacBook/iMac/MacMini, doesn't matter which port.
- Open Configurator in the 2nd MacBook/iMac/MacMini.
- Put the Monterey MacBook into DFU Mode (Hold Ctrl + Option + Right Shift + Power for 10 Seconds then let go of everything apart from Power - hold on to that one for a further 7 seconds)
- You will see a DFU square on Configurator if you haven't screwed that last part up, right click on it and click restore. It will restore using the restore image from the 2nd MacBook/iMac/MacMini.
- Wait for Big Sur to finish installing, all done, enjoy!