How to replace nextjs SDK with auth0-spa-js?

Greetings,
it may seem foolish to ask, but I am totally lost on getting started with implementing Auth0.
Since I want to create my custom atuhentication flows, I think the SPA version would suffice.
But I am not sure at all, if I would need to use e.g. the UserProvider from the Nextjs sdk?

Any hints on this, please?!