If we have special characters in username, necessary to use double quotes in configuration file /etc/ppp/peers/pppoX in param username
Reproduction steps:
set interfaces pppoe pppoe0 authentication password '33577204' set interfaces pppoe pppoe0 authentication user '004568262727535203262514#[email protected]'
Link to forum topic https://forum.vyos.io/t/pppoe-client-with-vlan7-deutsche-telekom-viperoptic/6502
LTS/Crux works properly