Could we get a clear / up to date guide on how to implement Email / Password user authentication?

Big thank you to Sebastian_Gadzinski who posted their process last year Email Confirmation Script for User Authentication via Email Address:

Continuing on from that discussion there was a lot of confusion on what the correct step is after a user gets the email to confirm their email address. Sebastian shows a step where the user is directed to a script that is hosted on MongoDB (it seems this is now a paid service? another user did suggest a a webpage that is self hosted) which holds the Realm Web SDK script via CDN with the additional JS needed to handle the confirmation. This however isn’t part of the docs on confirmation emails.
Can we get confirmation that if we don’t have a confirmation function for a production ready app (the other option on the docs) that this is the correct way to confirm a user email (requires a hosted script of some sort)?
If it is the correct way can we get a guide or link to resources that show how to implement this?
And if not could someone explain what is the correct way?

Many thanks in advance