I use router WiFi presence - previously I had a script running on my old Asus router which used a webhook to flip a virtual presence sensor (search AsusWRT WiFi Presence). Since I retired that I got a TP Link Deco mesh system which can use IFTTT to do both arrive and depart, so used the existing webhooks. Note that other mesh systems (Google for example, but others too) can't do triggers for both arrive and depart, they just do arrive only.