I used the .z domain bc it's quick to type and it looks "unusual" on purpose. The dream was to set up a web UI so you wouldn't need to configure it in the terminal and could see which apps are up and running.
Then I stopped working the job where I had to remember 4 different port numbers for local dev and stopped needing it lol.
Ironically, for once it's easier to set this kind of thing up on MacOS than on Linux, bc configuring a local DNS resolver on linux (cf this taiscale blog post "The Sisyphean Task Of DNS Client Config on Linux" https://tailscale.com/blog/sisyphean-dns-client-linux). Whereas on Mac it's a couple commands.
I think Tailscale should just add this to their product, they already do all the complicated DNS setup with their Magic DNS, they could sprinkle in port forwarding and be done. It'd be a real treat.