Hmmh? I thought NetBSD was the legacy/retro computing crowd. They still support (at least as 2nd tier architecture) SUN 2 with MC68K, which are more than 30 years old now. I don't quite understand the motivation for that, I must admit. If I would be curating museum machines, wouldn't I want the original software with it? You can't run modern software in a meaningful way on those ancient, quite limited machines, which have less RAM than today's CPUs cache.
NetBSD is a wonderful OS for embedded applications. Having support for a fully static port (the Sun2 port) and for old, generally slow architectures (m68k, VAX) means performance regressions don't go unnoticed, for starters.
I run NetBSD on a system with 24 megs of memory. I don't think this is possible with modern GNU/Linux - one would need an older kernel and something other than systemd, I think.