I felt this pain yesterday.

I use Open Core Legacy Patcher (OCLP) to run modern macOS on old Intel macs. The first time the computer boots after an upgrade (e.g. Sequoia 15.7.3 to 15.7.4), it is slow as a dog. Because the macOS upgrade clobbers all the OCLP driver patches.

By "slow", I mean each keystroke on the login screen takes about 20-30 seconds for the corresponding bullet to appear in the password box.

The login screen displays 13 bullets. My password is 18 characters long. (Scammers, don't get excited, it's a unique password that's not used anywhere else on the Internet...) So after 13 characters, I had no idea if the computer was actually working.

It seemed like there is a 6-8 character keyboard buffer limit. Or maybe I typed in my 18-character password wrong multiple times. I don't know. I would type 2 characters, then walk away, come back, then type 2-3 more characters. It took me about 4-5 attempts over 30 minutes to log in. Then I applied the OCLP patches and everything worked perfectly after that.