Heads up ...
https://www.reddit.com/r/kubernetes/comments/1mc73s4/bitnami_moving_most_free_container_images_to_a/
Think git acquired code, even with a bitnami, can be done - and should be done ... IMHO!
Devils are in the details ...
So your first hop was from 3.11.2 to 4.2.3 in a non-standard method of migratiing and upgrading.
See
https://moodledev.io/general/releases/4.2
Server requirements
where is says:
"Moodle upgrade: Moodle 3.11.8 or later"
Those point release differences make a difference ... and how far the hop does for sure!
So remind us what issues are you having now ... course backups from old server restored to new server has no users?
What was auth/enrollment methods on old server? If old server used manual then the backups that didn't have nu in their filename should have included users. And, since manual, then no issues. IF, however, the old server users authenticated via LDAP or Google or whatever, and that has not been setup on new server, then they might be there ... they just don't show!
Do the backup files you are using have 'nu' in their filename? That stands for 'no user'.
On old server:
mysql query of mdl_users for id,auth,firstname,lastname,email.
Same query on new server
Different?
'SoS', Ken