Well, nothing to keep hidden. DNSMasq, Syncthing, a tool which I developed that sends e-mails when things go wrong, etc.

The resulting infra is hidden, because it doesn't flow through any popular services or something. You can argue that Syncthing is using public discovery servers, but you can put it on a small VPS, and you'll have a complete off-the-grid installation of it, too.

I host it on an OrangePi zero, so it's unobtrusively small. It just vanishes somewhere at home.