$50 is decent enough for the case alone. The penguin may not be disgraced yet, I wonder if you can boot linux on it. I know gentoo and a lot of other distros support powerpc

IME NetBSD or OpenBSD are better supported options on New World Macs. I run NetBSD/macppc on a G4 Mac mini and it "just works" (tm).

OpenBSD seems to be the choice due to pre-compiled 3rd party packages. But I'm sure NetBSD works well too, and may even perform a little better?

There was Yellow Dog Linux, back then.

Fun fact yum comes from yellow dog