/etc/kppp.allow should contain commented-out example and/or one-line instruction on how to enable it; would be great to patch kppp to tell where to enable access for users ("see /etc/kppp.allow").
/etc/kppp.allow was excluded from package, because we have /etc/control.d/facilities/kppp
Well, so hope it's told in the docs (perfectly in the error message) what to do? OTOH while we don't have sensible group configurator it's harder to use group-based approach even with control ...but up to you.
Лучше по-русски пиши :-) В общем, достаточно создать этот файл /etc/kppp.allow, как он начнет работать.