Should I set up a password for mariadb.sys@localhost? I'm not clear what this user is for, but mysqltuner suggests I create a password for it.  I'm unclear if that's actually good practice, or if this is a limitation of mysqltuner simply because it's seen a user that it's not familiar with, that no exception has been coded for?
Running MariaDB 10.5.8
Thanks
Here's a great article that explains the purpose of that account.
This section of the article in particular explains why MySQLTuner is complaining:

It uses an invalid password (see the output of SHOW CREATE USER
above). This ensures that should the account get unlocked by mistake,
it is still impossible to login. It is thus recommended not to reset
the password.