Not all systems have access to create a VPN tunnel

[BPR02]

PeerStash cannot be used on non-linux systems due to the lack of /dev/net/tun. SOCKS5 userspace networking will be needed for those machines.

However, not all Linux systems support /dev/net/tun. For example, some container-based app platforms like Heroku and Google Cloud Run do not. For those environments, userspace networking mode offers a different way of running, where tailscaled functions as a SOCKS5 or HTTP proxy which other processes in the container can connect through.

https://tailscale.com/kb/1112/userspace-networking