I returned home for the holidays a few days ago and decided to update my parents' Mac mini, which was stuck on macOS 12 Monterey, to macOS Sequoia using Open Core Legacy Patcher (having successfully done so on other Macs).

Unfortunately, yesterday, I made a foolish decision to update to macOS 15.4.1 via OTA. After the usual reboots, I was unable to get past the login screen on the Mac mini because it crashed every time I tried to enter the password.

After some troubleshooting steps and reading the helpful and well-detailed Dortania's Open Core guide, I booted into recovery mode, mounted the EFI partition, and began editing the Open Core's config.plist. I first added the argument -igfxvesa to the boot args because I noticed that on the login window, transparencies were not working, so I thought it might be an issue with the iGPU.

I booted back into recovery mode and tried resetpassword to set a shorter password to at least attempt to gain access during the brief flashes of the login screen. However, this didn't work either.

After some Google searches, I found this post from the MacOS community on Reddit, that made me recall that my mother's profile picture is a Memoji, everything suddenly made sense.

After hours of trial and error, countless reboots, and an ever-growing sense of despair, I finally admitted defeat. As I type this, I'm reinstalling macOS Monterey, defeated, because I was unable to change my mother's profile picture.