My machine had no other Admin account #FML
theinstructional.com/guides/how-to-…
1. Cmd+R to enter Recovery mode
2. Enter my account password
3. Use Disk Utilities to mount the FileVault disk (Macintosh HD)
4. `rm /Volumes/Macintosh\ HD\ -\ Data/private/var/db/.AppleSetupDone`
5. `reboot`
[...]
6. Create a new temp account with admin privilege
7. Log in to that account & promote my existing one to Admin
8. Reboot
9. Log back in to that account & remove the temp one
10. Let out a big sigh
#NoteToSelf
apple.stackexchange.com/a/373103/2907