Modern Linux dropped support for a lot of old and niche CPUs.

And NetBSD is missing support for an order of magnitude more SoCs. I like NetBSD. I've run it on several systems in the past, and not just as a toy. I like the whole BSD family, and even deploy FreeBSD in production at work, and use OpenBSD on my home router. But NetBSD's claim as the most portable OS doesn't hold up these days.