I do have the idea of making an app it makes an account for one instance and uses that “log in with Google/apple id”. Then people can learn later that you you can join other instances or log in via web browser.
The server can be simple lemmy or mastodon server and the app can just be variant of Voyager or mastodon app. Someone need to get rid of copyright material then hard code an instance.
I would do it myself but I can’t get an AI to code apps
The other option is to have an app that browser based



Lemmy is more stable than what that graph makes it out. I’m not sure how easy it is to track fediverse since instances can pop up at any moment then grow or even the domain can change for an instance