The alternative that predates this is to this is to just tunnel ppp over ssh using pppd:

    pppd updetach noauth pty "ssh root@example.com pppd nodetach notty noauth" ipparam 192.168.1.100:192.168.1.2

I used this for many years before switching to openvpn. This does require root access on the host to execute pppd however.