As nobody in the non-english support forum helped I am translating my problem:
I updated to nc23 but the problem existed for a while I assume.
When I try to activate talk I get:
An exception occurred while executing a query: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away
there are some errors in the mysql log, most important should be:
2022-01-24 12:03:46 0x7f669009b700 InnoDB: Assertion failure in file /build/mariadb-10.3-ym4QNJ/mariadb-10.3-10.3.32/storage/innobase/dict/dict0mem.cc line 143
InnoDB: Failing assertion: dict_tf2_is_valid(flags, flags2)
InnoDB: We intentionally generate a memory trap.
and
Server version: 10.3.32-MariaDB-0ubuntu0.20.04.1
and
Trying to get some variables.
Some pointers may be invalid and cause the dump to abort.
Query (0x7f666809ef80): ALTER TABLE oc_talk_rooms ADD server_url VARCHAR(255) DEFAULT NULL, ADD default_permissions INT DEFAULT 0 NOT NULL, ADD call_permissions INT DEFAULT 0 NOT NULL
I think the problem is already explained here, unfortunately I do not understand whether there is already a solution to my problem there
https://jira.mariadb.org/browse/MDEV-17989?jql=text%20~%20"Failing%20assertion%3A%20dict_tf2_is_valid(flags%2C%20flags2)"
I uninstalled talk multiple times now and also restarted the server.