Upgrading mariaDB could brake the setup under certain circumstance.
Some users faced the situation that after upgrading their https://github.com/linuxserver/docker-mariadb docker image, Nextcloud could not start anymore. A closer look showed that the mariaDB server was caught in a loop during start. After a discussion on github (https://github.com/linuxserver/docker-mariadb/issues/22), we noticed that the mariaDB utf8mb4 migration (https://docs.nextcloud.com/server/14/admin_manual/configuration_database/mysql_4byte_support.html) had to do with this.
It seems that the following settings got default and by this deprecated (https://github.com/linuxserver/docker-mariadb/issues/22#issuecomment-422135366):
- innodb_large_prefix = true
- innodb_file_format = barracuda
- innodb_file_per_table = 1
Nextcloud could give a hint on their documentation page.