The SDF Public Access Unix System [1] might be the primary use case by the sheer number of users on a NetBSD cluster. :-) https://sdf.org/?status shows how many active users there currently are. I have counted user home directories with the fish shell as follows:

  dbohdan@ryo ~> count /arpa/*/*/* /udd/*/*
  27718

According to `stat -f %m%t%N`, 7519 users have had their home directory modified in 2024.

Outside of SDF, BSD and retrocomputing enthusiasts use NetBSD on their personal systems and servers. The portability and architecture attract some C and low-level hackers.

You can get an idea for how individual users run NetBSD, especially on modern hardware, by browsing https://www.unitedbsd.com/. UnitedBSD is a forum that acts as a hub for NetBSD users.

[1] https://en.wikipedia.org/wiki/SDF_Public_Access_Unix_System

Look into rump kernels; NetBSD is an interesting vehicle for research into virtualisation, micro VMs, also device drivers (the framework is said to be very elegant). I was also surprised to find out how simple it is to cross-compile the kernel from a different OS.

You can also look into pkgsrc; NetBSD is its parent project and pkgsrc remains very portable across many "alien" operating systems, from QNX to macOS.

NetBSD was also forked into, and retains many similarities with OpenBSD (the latter is pretty decent for both server & workstation; it is also my favourite OS of all time, even if I don't get to daily drive it). I'd like to give NetBSD a proper try in this area to get my own opinion.

I run a mail server on NetBSD. It’s refreshing to see how little is running on a NetBSD after booting it for the first time. I’ve also been tinkering with NetBSD on Raspberry Pi Zero devices; the built-in support for various add-ons over GPIO (eg, owtemp sensors) is surprisingly good.

Yes, mid weight embedded (bigger than RTOS, smaller than big embedded like commercial storage appliances) is probably its remaining commercial niche and it doesn't have the current marquee usages that FreeBSD has in various products and infrastructures but I think one of the longest running is at IIJ.

The 10.0 release is a massive improvement on modern hardware.

It's worth a look, for learning purposes if nothing more, as it is pretty clean and accommodating of research like the linked article.

It's also being used as a good virtualization host