The current oldest officially available openSSL version is 1.1.1, I have tried that one and was still unable to join my recently update server.
Have now tried 2 different unofficial 1.0.2d versions with no luck.
Have also tried the newest version 3.1.0, which doesn't install the .dll files you...
So, been running a Cata server for a couple years now, used the same client since the beginning.
Decided I had a need to play on it a bit and attempt to log in.
Client says its got a connection to the server but stops at "Authenticating".
Looking at the client logs I see a few errors have...
Just set the server up only thing i changed was the mysql port, the realm shows as "offline".
Edit: was able to fix the issue by using a different client... don't use CircleWow's MoP client, it's exe doesn't allow other connections to work.