I needed a VPN server.
Well, that’s not exactly true. I had a VPN server through software running on my everyday Mac. I had set it up years ago using voodoo tricks I gleaned from the Internet, and happily used it to protect my data whenever I was connected to a public network. It worked like a charm, but only if my desktop Mac was not asleep. This was not an issue when I had a Mac Pro that was always awake, but became problematic when I replaced it with an iMac that slept after 10 minutes. If I forgot to turn off its snoozing before I left the premises, I was out of luck. So I needed a better VPN server.