The communities are niche, but on the other hand Plan 9's internal code style, organization and the liberal use of a few small grand abstractions actually make

The communities are niche, but on the other hand Plan 9's internal code style, organization and the liberal use of a few small grand abstractions actually make it easier to study for hobbyists and researchers alike compared to a full modern Unix with all of its intrinsic architectural complexity and real-world cruft (not that OpenBSD isn't one of the best ones in avoiding this).