Upgrading to mariadb server 11.3 with official sources after upgrading to debian 12 broke root account

Upgrading to mariadb server 11.3 with official sources after upgrading to debian 12 broke root account, I got the following error :
ERROR 1045 (28000): Access denied for user 'root'@'localhost'
while accessing to any database, even a test one newly created.

Since I did not have time to investigate much, I was forced to do the following to get my production server back to operational state :
apt purge mariadb-client mariadb-server

-> change the version in the mariadb.list source file in apt
-> then I restored my backups and recreated the users with the passwords and grants, server-wide