I'd
recommend looking into running either OpenBSD or maybe NetBSD on them.
I know OpenBSD has a small enough memory footprint to fit on one nicely
(won't guarentee it's supported hardware though as I don't have any LX's).
Even Solaris 2.6 will be painful on one.
Be Classic- SunOS 4.1.4! NetBSD is a second-place contender, but good if you need all
the
new stuff, it doesn't have all the Sunny goodness, though.
Isn't SunOS 4.1.4 rather insecure in this day and age? Not to mention
harder to obtain.
Zane