¶Using tailscale to connect to Remarkable tablet

Tailscale is available in Toltec.

Toltec

# opkg install tailscale

I copied the systemd unit and /etc/default/tailscaled from my Arch Linux box to have something that I can systemctl start on the Remarkable. Had to tweak the startup options to use /opt/var as the runtime directories, since that seems to be patch-hardcoded into the Entware builds.

The Remarkable also doesn't have TUN device support in its kernel, so you need to use userspace networking. (Add ‘--tun=userspace-networking’ to FLAGS in /etc/default/tailscaled. I didn't need any proxy settings.)

Tailscale userspace networking

This seems to be enough to route SSH connections to the dropbear server on the tablet! Dropbear uses some old crypto algorithms, though, so you'll need something like this in your per-host SSH settings:

Host remarkable
    Hostname [tailscale IP]
    User root
    HostkeyAlgorithms +ssh-rsa
    PubkeyAcceptedKeyTypes +ssh-rsa

It looks like tailscale 1.28 will show up in the Toltec/Entware package repos soon. I think at that point I can use tailscale up --ssh to have tailscale take over the SSH server duties, which will mean no longer having to use the old crypto in dropbear.