Mixed format works just fine without Galera:

MariaDB [test]> select @@log_bin, @@binlog_format, @@wsrep_on, @@version;

+-----------+-----------------+------------+--------------------+

| @@log_bin | @@binlog_format | @@wsrep_on | @@version          |

+-----------+-----------------+------------+--------------------+

|         1 | MIXED           |          0 | 10.2.9-MariaDB-log |

+-----------+-----------------+------------+--------------------+

1 row in set (0.00 sec)

Is it possible that you have wsrep_provider set in your configuration, even though wsrep_on is turned off?

my goal was to have same configuration for all, but with wsrep_on = OFF and binlog_format = MIXED mysqd refuse to start.

but yes if you start mysqld with binlog_format = ROW and you switch to MIXED it's work fine.

after dunno about binlog_format = MIXED + wsrep_on = ON, if it's should work it's critical bug

I didn't mean starting with ROW and switching to MIXED to be a workaround; but I think if you have wsrep_provider configured, even with wsrep_on=OFF on startup, it's not that crazy that the server assumes it is going to be used as a Galera node, and thus refuses to start in a non-supported configuration.

I'll leave it to anikitin and sachin.setiya.007 to decide on the subject.

I agree with Elena - even if instance is started with WSREP_ON=0 - the parameter still may be changed to 1 later and Galera must make sure that binlog_format configuration is suitable.
So configuration should avoid enabling any Galera-related parameters to make sure that similar checks aren't performed.

The goal we can change it online (have this configuration), so why to refuse it on start, it's not logical.

I am agree you have to refuse to restart in this case :
@@wsrep_on = 1
@@binlog_format = MIXED

(and should be easy to change in code)

Maybe you don't see the interest right now, but with my tools (PmaControl) it's usefull. Else it's imply for me to change my.cnf and restart mysql and it's should be not required.

I'd think that "assuming that wsrep_on will be enabled eventually" is a rather strange reason to disallow MIXED. If galera only supports ROW, then it should refuse to enable wsrep_on run-time when binlog format is MIXED. But as long as wsrep_on is disabled, binlog format should not matter.

I found this bug by luck, because normally i mostly use ROW in 99% but was a bug with spider (see https://jira.mariadb.org/browse/MDEV-14019) I discover this one

I agree with your reasoning thus I verify this report as requested.