Enable Using Any Relational Database
As suggested by @firstname.lastname@example.org on Mastodon, we should look into allowing the use of SQLite because of how easy it is to use and doesn't require a database server to be installed.
I would follow this by suggesting that we should recommend PostgreSQL, but allow using any popular relational database management system. The community
fastify-sequelize plugin for Fastify may be worth looking into because it enables connecting to SQLite, MySQL, and Posgres (though I'm really not a big fan of Sequelize).
Side note: if we enable using SQLite, we should also enable the ability to disable federation so the server/SQLite database doesn't get overloaded.