Solaris 7 is the last supported solaris release on an IPC. However, you
should be prepared to not use X, and fully load it with whatever memory
you have.

I have found better performance with the BSDs, NetBSD and OpenBSD seem
to work acceptably.

I gave up using the CD, and netinstalled them.
Using CD-R's in a CD-rom drive of the sort of age suitable to work with
a computer that old is a tricky experience. it may work, but dont count
on it.

You *can* install linux, but on an IPC, i dont recommend it. It works
fine on the more powerful boxes, but on a 25Mhz SPARC I, it seems even
slower than Solaris 7.

If you are going to try linux, try Debian Woody. Its the only one I have
found which seems to install relatively cleanly. Even Sarge seems to
have problems.

Forget SunOS unless your doing the antique computer thing. its very slow.

Of course a much better solution would be put in an 8 bit framebuffer
and use it as an X terminal to a bigger computer.
SLXT runs like a charm on these old boxes, and an IPC is even looks
compact on the desk.