image depicting the tailscale client on a phone in front of the tailscale client on a laptop

Tailscale, specifically the server portion (which isn't Open Sourced), is used to initiate P2P VPN connections between your hosts.

There's a great alternative whose server is fully open sourced, it's called NetBird. There's also an open source server that can be used by the Tailscale clients called Headscale.

I've been meaning to migrate from Tailscale to NetBird for a while now, and at some point I had the NetBird clients installed on all my servers, but the NetBird DNS conflicted with Tailscale's, and at the time I couldn't continue so I disabled NetBird.