I'm confused which one is better. I know that MariaDB is a fork of MySQL but what does the Laravel community use? Is MariaDB better or more modern? Which one would you recommend and why?
They are the same. Even in Java the same connector works with Mysql and MariaDB, the JDBC Driver for MySQL.
To add, for a larger Enterprise setup you would want MySQL. But for most things people are going to do in laravel there is really no significant difference. Innodb the same.
However I would suggest you read the specs of both for yourself.
What's good with Laravel is that you can use both without pb if you don't want some specific functionality like partial index that does not exist in mariadb.
Personally I use Postgresql mainly for reliability, 0 data lost in 20 years, in case of "crash of the server", it'll be more difficult to retrieve your data with mariadb