[senttoschool]

I would personally go with Rails backend + Next.js front-end. You don't need to use Next.js to build your backend. In fact, I would never use Next.js to build my backend unless it's for something simple.

A lot of things don't work as well with Next.js' serverless backend approach such as database connections, websockets, or even something as simple as a cron job done on the server.

Serverless backends tend to make things more complicated when you're trying to build an MVP - unless cheap scaling is part of that MVP.