That's great! If you'll find time, please let me know the sequence of installation and configuration changes you have used to make it work. It will help me to produce the updated document. As of now, it looks like the PAM module was removed from FreeRADIUS 3.X.X and in order to install it you have to build it from source code. Doing that works, but the FreeRADIUS is not installed as a service. I was planning to reach out to developers to get their take on this issue. If you have found a workaround, I'll be keen to hear about it.
Cheers,
Vladimir