With either of the latest MariaDB LTS releases, 10.6.13 or 10.11.3, if (and only if) you are running Galera Cluster with it, a change was made where GET_LOCK() errors out instead of being silently ignored as it was previously:
This version of MariaDB doesn't yet support 'GET_LOCK in cluster (WSREP_ON=ON)'
This breaks at least RT 5.0.4 (and MediaWiki, and probably lots of other stuff) pretty badly.
This seems to be the MariaDB commit introducing the change.
While this is arguably a Galera issue rather than an RT one, it’s something RT might need to investigate a workaround for – other than moving to a standalone database server, staying on 10.6.12 (not ideal long-term, but is what I’m doing now), or moving to another DB engine.
There seems to be some discussion on this in MariaDB’s bug tracker.