Need Help Creating Trigger For When Entity Has Not Changed Over A Time Period

I’m trying to create an automation that runs when a Raspberry Pi is no longer on the network. I have a Raspberry Pi in my attic that tracks ADS-B air traffic, and from time to time it drops off the network, I am trying to create an automation that detects when this happens. I have the RPI Monitor running and the condition I want to create a trigger for is when the CPU hasn’t changed in XX minutes shown in the screenshot below

When it drops off the network the CPU flatlines at it’s last reading, so I’m not really sure how to set that up.

A nudge in the right direction would be appreciated.

Check here for a starting point
Display recently triggered automations - Share your Projects! - Home Assistant Community (home-assistant.io)

Or you could ping it from HA. That woiuld give you a binary sensor that’s on or off to use as a trigger.

looks to me like you have an entity on it already that stops changing. so i think you want last_changed. if you have an automation that stops getting invoked you can use last_triggered as @jeffcrum posted. you can create a template automation that directly triggers off of last_changed being longer than your threshold.