Can you provide more from your /var/log/auth.log.
I tried a local test with a non-existing user, and this is what I see in the log (on ubuntu 20.04 instance)
Oct 23 16:23:48 vps-34 sshd: Invalid user adminxxx from 22.214.171.124 port 35382
Oct 23 16:23:50 vps-34 sshd: pam_unix(sshd:auth): check pass; user unknown
Oct 23 16:23:50 vps-34 sshd[...