I like the idea and how it's presented. Yes, I think this might work.

Then I asked myself why we need it and if we really lack tools to solve it.

What I mean is: Instances can already close themselves for new registrations. Or they can make their signup process less easy (for example by requiring a written statement why the user wants to join specifically them).

If instances don't do that, would they opt into your system instead? After all, both depend on the instance to want to grow slower. In both cases, I'd expect those instances to become the biggest who simply accept any new signup for themselves.

this is a great idea. If you want DM and I'll see about writing the standard and making the PRs for both the backend and official frontend

Thoughts?

I haven't tested with 0.18.3 to see if new features were added to front-end lemmy-ui, but based on my experience with earlier 0.18 releases... the "Sign Up" page of Lemmy needs to have a custom message added for each instance basically introducing the instance from the admins. The experience is pretty bad... on my instance I have registration closed and lemmy-ui still just presents "Sign Up" links and even the form. I think it's pretty important to get this in the back-end now so that the evolving independent front-ends all support the custom message shown above/below the Sign Up form..

Seems like something that shouldn't take a lot of coding to get added (admin screen has place to create custom messages like "Legal") that would be a good lemmy network-wide focus on the newcomer experience.