There are quite a few gems in the Tailscale blog. I've come back to their posts about NAT traversal (https://tailscale.com/blog/how-nat-traversal-works/ https:/

There are quite a few gems in the Tailscale blog. I've come back to their posts about NAT traversal (https://tailscale.com/blog/how-nat-traversal-works/ https://tailscale.com/blog/how-nat-traversal-works/) and how Tailscale works (https://tailscale.com/blog/how-tailscale-works/ https://tailscale.com/blog/how-tailscale-works/) a few times, not necessarily for the technical content but for how well they're written.