I'm in the process of uploading an image of jessie for the RPI 3 to https://sourceforge.net/projects/uronode/files/?source=navbar

If you wish to give it a go, that's where it'll be in approximately an hour from this post. It's made from the kit sold near the TAPR booth at this year's Hamvention at Dayton. You'll need to edit files in /etc/ax25, /etc/postfix, and the file /usr/local/bin/ax25 other than that it should be ready to go. I did notice the main repositories that came with it failed but an apt-get update fixed those issues.

It was made using the uronode-pi.tgz script available in the tools section of the same sf.net site.