OK, I did it, I'm embarrassed...

[Sarcany]

So long as it's not a M1 or T2 iMac and you haven't opted to tie your login to your Apple ID and you're not using FileVault, you can do the .AppleSetupDone trick in Single User Mode to create a second admin account and then use the new account to reset the PW on the old account.

...Catalina can complicate the operation. Running something pre-Catalina?

http://www.theinstructional.com/guides/h...-assistant