somehow I forgot that existed.

Perhaps it was its mention of being a demo implementation here: https://twtxt.readthedocs.io/en/latest/user/registry.html#registry So I though it wasn't really active.

Anyway, I think that's a good idea.

Is there something similar available on Yarn? Sorry for for asking if that was mentioned recently.

I think that the clients may help you to submit your URL to these directories, and also to get a view of the twts in them.