Your best bet would be to use something like Supabase, which simplifies all the backend stuff. Get deep into the docs and use Claude to figure stuff out.
When does the rugpull happen? I see using a third party auth as a suicide pact. What stops Supabase from sending out the usual email that "they're proud to have been acquired?"
You can actually self host Supabase, that's really the whole point: a Firebase alternative that you can host yourself. Obviously you can use their hosted service as well.
I think supabase is open source such that you can (and many customers do) self host with no additional cost and with complete control.