I have Tailscale directly installed on the host and I don’t use Mullvad so I haven’t tried that setup myself.
Looks like you would need to set the TS_EXTRA_ARGS
environment variable in your container to --exit-node= --exit-node-allow-lan-access=true
with the exit node name or ip of the Mullvad node. I haven’t tried this myself though.
I agree with the headphone jack, but the only Nexus with a microSD slot was first one, the Nexus One.