PPPoE server supports setting the MPPE preferences, it is implemented as node with leafnodes for require, prefer and deny. This will render a wrong Accel configuration as it will be "None" if specified.
+pppoe-server { + ppp-options { + mppe { + deny + require + } + } +}
it must be:
+pppoe-server { + ppp-options { + mppe require + } +}
The first version renders the following AccelPPP configuration:
[ppp] mppe=None
Accel docs: https://accel-ppp.readthedocs.io/en/latest/configuration/ppp.html?highlight=mppe