I always use a custom server (even express will work) with next.js, because I found the middleware and edge stuff a load of overcomplicated BS. Client side works like regular react app, SSR for any pages where the initial props are just populated from the server site is easily controlled, and the whole system is simple to reason about. There are other frameworks out there to do this now, but I'm comfortable with this and it just works, so no reason to change.