Why is ns2 in the garage? Everything you said makes sense except for that.
Geographical distribution. If the left half of my house is destroyed by natural disaster, I’ll still have a working name resolver on the other side!
Seriously, it’s just because I may do something else on that Pi that I want it on that side of the house. It’s my only garage Pi. My main internet handoff is in the garage, but my main “datacenter” is in a basement room on the other side of the house.
It’s all for fun. :)
I use RPIs as "data collection" units. I have one RPi outside with a cheap SDR to pick up all the neighbor's weather stations, which I dump to a MQTT queue and use to populate weather data in my home. I use another to collect GOES satellite images.
I have 3-4 RPis that act as "Digital Ham Radio Hotspots", basically bridging my local ham radio via the internet to other stations. I use an RPi 4 as my "to-go" computer when I do ham radio in the woods. I use an iPad as a screen, and it works just as good as a laptop.
I have an RPi sitting in my garage as a second nameserver. The primary nameserver is in the house "data center".
I have an RPi plugged into my stereo receiver as a streaming device that lets me stream audio from my phone to the stereo.
I have 4 RPis connected togehter in a k3s cluster, for fun. IT doesn't work great. :)
I have two PiKVMs. They are truly awesome.
... I think that's it.