I am thinking about switching from pfSense to VyOS for my home network router. I have a slightly unusual setup in that I get my broadband from one provider but get IPv6 connectivity and static IPv4 address from AAISP over a L2TP tunnel: https://www.aaisp.net.uk/broadband-l2tp.html
This is plain L2TP, unencrypted over UDP without any IPSec.
Now that I have a semi-usable VyOS I have tried setting up a L2TP tunnel, however I don’t see how to configure the ppp username and password? Also, I am not sure it is backwards compatible with L2TPv2 (RFC2661)?
L2TPv3 is a different thing. What AAISP does is normal L2TPv2, the same that people use in L2TP/IPsec, just without IPsec.
The bad news is that we don’t have a CLI for L2TP client in VyOS yet. The good news is that you are willing to test it in realistic settings, we can add it—the main reason no one did is because there was no one interested in testing it.