ppp

To connect using legacy pptp:

sudo apt install pptp-linux

Issue:

MPPE required, but MS-CHAP[v2] nor EAP-TLS auth are performed.
sent [LCP TermReq id=0x3 "MPPE required but not available"]
rcvd [LCP EchoReq id=0x0 magic=0x5dd9b546]
rcvd [LCP TermReq id=0x3 "peer refused to authenticate"]

Solution:

# client    server    secret    IP address
john      provider   "secret"   *