The Unifi cloud stick isn't that much more expensive than a PI, and is probably the least amount of work to set up a dedicated controller.

I use an Atom based PC stick that I had lying around to run the controller (on Windows) and it works great.

I mistakenly thought the cloud key ran a lesser version of unifi than the distribution found on their website, however googling around implies it's the same version. So I suppose budget for a cloud key or a pi. A raspberry Pi 3 is 64 bit, runs Fedora natively and can serve up other functions beyond the key. So I lean towards the Pi but if they're functionally equivalent I suppose it's down to personal preference.

I tried putting it into a docker container, but in the end didn't want to deal with the complexity -- bought a key. Does the VM/Raspberry PI get you anything the key doesn't?

A Raspberry Pi probably won't do. The controller requires MongoDB which itself is no longer supports the 32 bit architecture which most RPis are running on.

Pi 3 is 64 bit and natively supported in Fedora.

https://fedoraproject.org/wiki/Architectures/ARM/Raspberry_P...