Sometime between 1.4-rolling-202301210856 and 1.4-rolling-202302110748, VyOS has started rejecting PPPoE usernames containing a '.' character.
In the UK at least, convention amongst several ISPs is to use PPPoE usernames of the form [email protected].
[edit interfaces pppoe pppoe0] malcolm@kylerhea# set authentication username "[email protected]" Username is limited to alphanumerical characters, -, _, #, and @ with a total lenght of 128 Value validation failed Set failed
(the error message also contains a typo: "lenght"!)