Headscale [1] has a stronger claim to "free version of Tailscale" - it's literally a self-hosted version of Tailscale's coordination server. It's even compatible with the Tailscale client.
The problem with Headscale is that it has absolutely no documentation. All of it is described in relation to Tailscale, which is what I don't want to use. Here are the Tailscale features we have, here are the differences with Tailscale. It's very weird.
