I use postgres for very simple apps. I have a Dockerfile I use in my boilerplate repo. It takes a single make cmd for me to build, start and run migrations. Its as simple as using sqlite.

Or you can run postgres on the same machine as the application, which lets you much more easily migrate if the time comes when you need to scale to multiple application servers.

There's a world between "local file" and "network DB server", running a DB server locally has lots of benefits from being able to easily query from outside if needed to forcing you to consider concurrency without the latency overhead of a network hop.