It’s really hard to find servers which actually use alternate auth servers like ely.by or littleskin.cn like as actual auth servers and not just a skin server.

I think this is largely for two main reasons.

1. It’s way more complicated and less easy to set up authlib-injector on a server
2. There’s pressure and stigma in English speaking Minecraft communities not to.

If it were as easy to setup on servers as it is on the client, we might see servers that use it in non-English countries like Brazil, Russia, and China. As it is though it’s too complex and a password mod that remembers your client username is simpler to set up.

Offline mode servers are way less common in English speaking communities for the second reason. I really wish more people would build them and tell the neoliberals in the Minecraft community whining about piracy to shove it.