You can generate the coin movement operation in the air gapped machine, write it down on paper, and then use a normal, connected computer to transmit it to the network.
The private key never left the air gapped machine, with this method.
I keep getting calls from recruiters offering 30k€ in North Spain, but they are hurting, as nowadays everybody is getting better deals thanks to remote work.
>switching ISPs may throw your internal network addressing in disarray which can be either a pain or a massive problem
Those are what ULA's do. A local router that provides global addresses and ULAs solves all your problems, and that's the default behaviour of OpenWRT (and probably other routers).
If you want traffic to not leave your local network, listen to your ULA (fd00::whatever) and call it a day.
My home server and several machines are directly connected to the router via ethernet, and it also offers WiFi in the house.
The router offers regular IPv4 NAT in a /24, and passes down GUA and ULA /64s. It also runs a wireguard VPN, DNS and DDNS, and acts as firewall.
My home server runs Ubuntu and runs a lot of stuff, like storage, Nextcloud instance, torrent, internet radio, UPNP media share to the TV, and more. Mostly docker containers and traefik for HTTP, managed with ansible playbooks.
Considering I got both of those devices from the recycle bin, I'm very happy how they work.
There's plenty of bluray drives still manufactured, mostly on each modern console. I hope I can find a working in 20-30 years, my PlayStation 1 is still working strong :D
Probably IPv4 is on CGNAT and Sprint doesn't keep the logs of the translation.
On IPv6 there's no NAT, and there might be a deterministic relationship between subscription and IP