I got it sorted out by mistake (i hit enter to early while trying to enter MariaDBs shell - without a password). I entered a mysql password during installation, but it seems like this didn’t get set in MariaDB. I started MariaDB as root with no password entered and could then change the root passwort to what it was supposed to be.

Although this thread is quite old. I have the same problem. The installation ran without hiccups. The mentioned logs don’t show any problems. my MariaDB only contains the root user. @fpuser: Have you found a solution?