That's the problem with groups like this. Are we really going to get back to the point where we can just type in our own identity providers? Stackexchange was the last big site that I used which still had OpenID support and it had less than 1% usage:

https://penguindreams.org/blog/the-decline-of-openid/

Seems like the biggest problem with OpenID is they had a marketing push, multiple sites (like google, yahoo, and facebook) bragged about it. The problem is large companies could grab about providing OpenID, while not allowing logins from any other OpenID provider. So you needed an OpenID account/login per provider... which is useless.