Ask HN: How to bypass root passsw/passphrase in Ubuntu 18 GRUB for beginners?

There's user apps/desktop locked by a passphrase on an Ubuntu 18.04 after multiple unsuccessful attempts to enter user password. I can get into GRUB menu only, for root console it requires passwords. In detail the situation is described here [1]. I was curious how geniuses and PhDs of CS, as everybody here functionally is, can handle this situation.

[1]https://ubuntu-mate.community/t/is-there-a-way-to-change-root-user-password-in-grub/25204/5