If Linux will run on a Mac may depend on the hardware!
For example, SuSE's 7.x seems NOT to run on a Mac G4 if
it was made after January 2001, and runs at 533 Mhz or
better. I happen to have exactly that model, thought I'd
be safe even though I did not know the Mac, since I was
very familiar with Unix, Linux (esp. SuSE) and even the
NeXT. I'd expected OS X to look like NeXTstep. It DOESN'T.
It seems that any smaller, i.e., slower, Mac of Jan 2001,
or anything earlier (but not too far back) WILL run SuSE's
7.x. I was lost. So I've used the Mac very little --
haven't even gotten around to finding out how to create a
Root user (!!) (( And the doc.s from Apple do NOT tell
you how !! ))
I'd be very glad to hear if someone knows if SuSE, or
anyone else, has gotten around the hardware problems for
Linux on a recent G4. The last I've heard, the problems
were with the newer graphics cards and ethernet.