In theory you could run Headscale, but you're really working against Tailscale's intended design at that point, and Iroh was built for this from the ground up, so what is Tailscale buying you?
> there is one giant "network" of all your nodes
From what I understand they're saying, the point is that you get easy connections to things that aren't "your" nodes, sort of like allowing me to connect one of my tailscale nodes ad-hoc to one of your tailscale nodes, when our accounts are not related in any way prior to us doing that, and without me having to allow your node onto my network or you allow one of mine onto your network and have to deal with the specialized ACLs for that, since it's just a direct connection between two nodes.
The similarities are in an application lib to connect, and that tail net IPs correspond to device keys like in Iroh. The service using the Go library has its own Tailscale identity.