I have an old Mac 6400 that I want to use as a server. Ruby for the old Mac
OS seems to be moribund so I need a new OS for the old beast. There are too
many to choose from. I've made a, probably non-exhaustive, list of
candidates. Is there some choice that really stands out?

NetBSD
SuSE
Debian
Yellow Dog (The Red Hat of PPC distros)

Yeah, I know I'm mixing OSes and distros.
-- 
When I was a boy I was told that anybody could become President. Now I'm
beginning to believe it. -Clarence Darrow, lawyer and author (1857-1938)