[varenc]

The CLI version of the Tailscale client on macOS can be compiled from source and installed without the app store:

   go install tailscale.com/cmd/tailscale{,d}@latest

https://github.com/tailscale/tailscale/wiki/Tailscaled-on-ma...

So fully available in situations with limited connectivity. The GUI version of the client is closed source though, and it's available as a package or from the app store.