Tailscale android app doesn’t mention the online or offline since status of devices.
The mobile UI is deliberately simplified. We experimented with an activity dot (which can still be seen in the Network Devices list of the desktop apps) but it caused more confusion than actual user affordance.
Active status can be seen in Tailscale from a mobile browser if there is a specific need for it.
a simple green dot to indicate online and red dot to tail scale offline could have done the trick.