In order to be able to get connected through PPPoA you will need a special version of ppp patched for PPPoA support. This support is provided by a pppoatm.so "plugin" which is - unfortunately - only available for ppp version 2.4.0b2 (The "standard" Bering ppp version is 2.4.1). The pppatm.lrp package is nothing more than this patched version of ppp 2.4.0b2 which was developped by Michael Mitchell. This package will replace the ppp.lrp package provided on your Bering floppy.

Note: pppd will appear as 2.4.0b1 in syslog but it's really pppd 2.4.0b2 !

Boot your Bering floppy image. Once the LEAF menu appears get access to the linux shell by (q)uitting the menu. Edit the syslinux.cfg file and REPLACE the pump entry by pppatm in the LRP= list of packages to be loaded at boot. Check the Bering installation guide to learn how to do that.

Your syslinux.cfg file will then look like (adjust to your tastes):

display syslinux.dpy
timeout 0
default linux initrd=initrd.lrp init=/linuxrc rw root=/dev/ram0 boot=/dev/fd0u1680:msdos
	PKGPATH=/dev/fd0u1680 LRP=root,etc,local,modules,iptables,pppatm,keyboard,shorwall,ulogd,dnscache,weblet

The pppatm.lrp package is available here.