NC24 User Migration Documentation

Im really excited about the new user migration. The marketing/sales pitch sounds super fantastic marketing amazing!!!

Where’s the documentation so people can actually use it?

https://apps.nextcloud.com/apps/user_migration

Is this what Im looking for?

Yes. They even put a documentation for the app developers:
https://docs.nextcloud.com/server/latest/developer_manual/digging_deeper/user_migration.html

So probably it is not supported by all apps yet.