We do also use their auth, storage, api, etc. But even if you just want to host a postgres db it's still worth checking out I think.
It's managed postgres, 2 free db's, connection pooler, super easy read replicas (requires a larger paid instance), backups, lots of tooling/dashboards/advisories, cli for running locally during development, database branching, backups, fdw, and lots more. All of it open source.
You can turn off the data api's etc if you just want to connect directly: https://supabase.com/docs/guides/database/hardening-data-api...
but using supabase for auth, this means if need to play w RLS but i had a very simple db design and didn't want to include rls yet. supabase won't let me do it afaik.
so i switched to using ory/kratos ultimately.
also q, how heavily are we dependent on supabase ecosystem if all we want is the db?
edit: yes that should be possible that's what op mentioned
Supabase is designed to work like LEGO, you add the blocks you want, and we keep everything as modular as possible so that you can combine it with other services like kratos if you prefer