myVesta

My 2 cents - if you don't want notifications for backup finished OK. Find lines which send mail message (script: /usr/local/vesta/bin/v-backup-users at line 78), and update condition like this: if [ "$FINAL_STATUS" != "OK" ]; then if [ ! -z "$NOTIFY_ADMIN_FULL_BACKUP" ]...

It is good idea to update that script to send notification only if backup fails for any reason
So if "status=OK" - don't send mail

How did you even enable "root" login to phpMyAddmin, since it's disabled by default? I did not do anything special :) root@localhost is not disabled - you can use shell cli access with that user. Just logged into phpmyadmin with root user and password from .my.cnf file phpmyadmin use loca...

Also this can bellow be cause, but I have MariaDB and phpMyAdmin on other servers, and not getting that error.

Since 10.4 MariaDB uses mysql.global_priv and older versions use mysql.user tables to store user information

Login to phpMyAdmin as root user:
click on User accounts - throws error:
Env version: Fresh install on Debian 11, MariaDB 10.5.19, phpMyAdmin 5.0.4deb2+deb11u1