Of course ther was NetBSD for all MMU-Amigas with 8MB of RAM in the 90s.
Not only was, but still is. Latest NetBSD release still does support 68k Amigas (though 16MB of RAM is minimum these days).
There's also experimental PPC-native version for Amigas with Phase5 CSPPC/BPPC cards, and it sort-of-works.
