I have the same problems.
1) The first one was solved adding the MARIADB_AUTO_UPGRADE variable (1).
2) No application can connect to the ddbb. I have several data bases, but all appplications get the same error:
From phpmyadmin: "mysqli::real_connect(): (HY000/2054): Server sent charset (0) unknown to the client."
Also very similar from Nextcloud: "SQLSTATE[HY000] [2054] Server sent charset (0) unknown to the client."
...
The log of MariaDB just get the same entry for every connection attemtp:
"[Warning] Aborted connection 270 to db: 'unconnected' user: 'unauthenticated' host: '172.23.0.1' (This connection closed normally without authentication)"
Anyone has been able to solve this connectivity errors??
EDIT:
I have installed a previous version as suggested by Autchirion and it is working fine.
At least Nextcloud and phpmyadmin, I have to test Home Assistant.
I have used REpository: mariadb:11.2.3 as Autchirion already mentioned.