I had a classic OpenID server and every website I use to authentication against using it has gotten rid of OpenID support. Stackoverflow was the big one. I haven't tried OpenID Connect yet.
By the way I wanted to say I read that blog post a bunch of times while trying to put together that software! OpenStreetMap and GnuSocial may really be everything on the internet now.
I'd almost sign up for a website at this point just to get a chance to use my OID provider...
https://battlepenguin.com/tech/the-decline-of-openid/