but that refers to the battery level I think. I have found older posts with entity_id: binary_sensor.tradfri_motion_sensor but that does not seem to work and is not viewable in the automation editors state browser.
If you use the IKEA gateway, it is impossible to detect motion from the motion sensors. Not HA’s fault, it is the way IKEA designed the system. You need a third party ZigBee coordinator (zigbee2mqtt, ZHA, deconz) to use them as motion detectors.
to share my experience:
last april/may on my very first installation of Home assistant on the RPi3 i had the signal of the presence sensor shown on the home assistant, wich worked fairly well and i am using the ikea tradfri gateway.
right now i only receive the battery level, which is nice to know but not so useful
this tell us there is a possiblity to go through the ikea gateway to have the information we need!
i am a noob on the domaine but if someone is willing to share a bit of time to try to debug it, would be a great help for the community.