AFAIK NetBSD runs just fine under 030+ Amigas. Don't expect any usable X system for it though.
For PPC I can only recommend Debian PPC (Apus) since I have done it, but it's really a pain in the a$$ to setup

(OFC Only if you have hardware that it's compatible like BPPC/CSPPC with BVision/CVisionPPC)
Just to mention some stuff...
- Installing Debian is nowhere documented as a guide.
- Most peepz that successfully done it, were on A4000D with CSPPC with some info written in German websites.
- Even from some of the steps, the paths and repos for Debian have been moved to other servers and paths which will make you search like the nub and sometimes just guess

- To be able to install you DEFINITELY need to acquire specific PCMCIA network adapter that works with Debian (for example NONE 3com cards work). (Unless you can do it with only the CD's that I haven't tried)
- Apart from all this, you need to download Debian and boot it with parameters that are not documented anywhere (so according to your setup it might need a twinkering to the Bootstrap command)
- After successful installation, you need to edit the repos list in Debian cause nothing exist in the predefined paths
- Even when you install and everything runs like a charm like mine... you'll realize that you wasted 2 days installing Debian which is totally cool, but it's Kernel doesn't support Permedia and need to recompile a new one (that step I haven't done) but it works fine without it. Gnome is really slow but it works
Just for proof I'm attaching 2 photos:
