SKRUF_MAN has contributed ISDN4K packages for Amigo2, which are available for testing here:
http://amigolinux.org/download/Amigo2/contrib/isdn/
A configuration utility is also included.
Here's the Mini HOWTO:
1. make ISDN devices with makedev.sh
2. installpkg isdn4k-utils-i386-1.tgz (or isdn4k-utils-i386-1_hisax.tgz)
3. tar zxvf conf-isdn-account-1.6slack.tgz and run ./install script
4. run conf-isdn-account to setup ISDN card and dial in account
Feedback is welcome.