Hello,
I am using Mattermost 10.1.2, and since then, because I am using MariaDB, I haven’t been able to update the server. This is because in newer versions, due to database incompatibility, I faced issues with notification delivery.
For a while now, I’ve been receiving a notification on the mobile app stating that the server version needs to be updated and that some services, like notification delivery, might be affected.
Now, in order to update to the latest version, I need to migrate the database from MariaDB to PostgreSQL first.
The official Mattermost documentation is a bit complex for me.
Is there anyone here who has done this before and can guide me through the process?
As far as I know, MariaDB isn’t supported at all (maybe it was years ago, but in the last few years it wasn’t). I’d recommend to migrate to MySQL first, before migrate to PostgreSQL (e.g. because the migration script supports MySQL only).
For MariaDB → MySQL: https://blogs.oracle.com/mysql/post/how-to-migrate-from-mariadb-to-mysql-80
For MySQL → PostgreSQL: Automated PostgreSQL migration - Mattermost documentation
For now, I don’t have much real-life experience with these types of migration, though.
What are the points in the docs that are too complex?
You might consider creating a new Mattermost instance and following this excellent guide to migrate your data over (using mmctl):
Full disclosure, I’m about to self bump my own bug report 
Hopefully you have better luck than me, as I’m facing a bug with mmctl export: