Private VPN IPs: special private IPs, generated in a public server, with encryption and secured access, that offers to users a dedicated tunnel through an internal private IP range, directly to your home devices. Each point / device will have its own IP, in the same range. This is what Tailscale is using.
Using Tailscale doesn’t mean your Umbrel is fully accessible on clearnet. Only you have a dedicated private access using a faster connection than Tor.
Hope that helps✌️