The new command to flush the privileges is:
FLUSH PRIVILEGES
The old command FLUSH ALL PRIVILEGES
does not work any more.
You will get an error that looks like that:
MariaDB [(none)]> FLUSH ALL PRIVILEGES;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'ALL PRIVILEGES' at line 1
Hope this helps :)