A small pair of vernier calipers. I don’t use them a lot, but sometimes they come in very handy.

My router is called Jupiter, everything connected to it is named after a moon. Callisto, Ganymede, Thelxinoe, Kallichore are what I’m currently using.

You can host a Firefox sync server yourself. You could run that on something like a Raspberry Pi in your local network. If you need remote access, use something like cloudflare tunnels (although I guess that’s something else to be paranoid about).

That’s why I don’t let every device decide individually. I know my router (FritzBox) prioritizes the pi-hole (it’s even called “preferred” and “alternative” DNS-Server in the UI)

I have my pi-hole setup as the upstream DNS in my router, with cloudflare as a secondary DNS. That way, all my devices always use the router for DNS (since that’s what is advertised in my DHCP) and the router then uses pi-hole if it’s available, or cloudflare if it isn’t. But the individual device doesn’t get to choose between different servers.

I’m guessing it’s about documenting the assembly of safety-critical components. If some part of, let’s say an airplane fails because a bolt comes loose, the manufacturer wants to have a paper trail attached to it to prove that this specific bolt was indeed torqued to the correct spec. Connecting the wrench to the network could make this documentation much easier.