As of my knowledge, you can’t update the MariaDB version in free hosting. You have to wait until the system releases an update. which probably won’t be soon.
Since Moodle 4.2, it appears that Moodle requires MariaDB 10.6.7 or later. The free hosting platform is currently using MariaDB 10.4, which is supported by Moodle’s 4.1 LTS release, so try looking for plugins that support version 4.1 (and optionally make sure that your Moodle installation is also on that version, if your site works regardless I suppose you can ignore this).