Hello everyone,
I have successfully installed debian to my C860.
The steps are very simple.
1) Download Angstrom from angstrom autobuild area, anything is ok after 2007.12-r16.
Choose alt-boot imagesm so you don't have to download alt-boot.
link here :
http://www.angstrom-distribution.org/unstable/autobuild/2) Install angstrom.
3) After installation, boot angstrom, enter boot-password, then you can boot from sd card
4) reboot normally. copy /lib/modules to a storage card.
using alt-boot.
Do the following steps in linux-desktop.
4) download zdevil eabi-rootfs.
5) using linux desktop, create 2 partitions in sd card.
6) untar zdevil rootfs to partition 1 of sd card.
7) change partition 2 to swap.

do a mkswap on partition 2.
9) mount partition 1. change directory to /sbin
10) do a ln -s init init.sysvinit.
11) from the storage card in 4, copy to rootfs sd card the contents of /lib/modules.
Now insert the sd card to you 860.
12) boot using alt-boot choose sd card to boot and you have debian.
BR,
Felix.