[lunatic]

If you don't want current updates there are more options. I recommend neglecting any current maintenance, because this is really old hardware. NetBSD should in theory work, but the quality has suffered over several years now. There is no real guarantee that current NetBSD will even boot. The old days of NetBSD supporting everything but your kitchen toaster are long gone.

When you look at older systems, then you could have a fun retro machine. NEXTSTEP or Openstep might be nice (single CPU SuperSPARC only). Good candidates for older Sun systems are Solaris 2.4 or SunOS 4.1.4. You won't be doing anything productive either, but you will have a fun restoration project.