We recommend Firebase, here's
why. In a nutshell it is a more cost-effective option and it works well out of the box and simplifies things like sending emails, using google sign-in and google analytics. But Supabase is also a really good alternative for you to explore, just keep in mind that they charge $25/month per project on the paid plan (which you need if you want backups or have more than 2 projects), whilst the cost is zero in Firebase (even on the paid plan of Firebase until you exceed generous thresholds).