Presence Detection IS hard.
IFTTT is slow, prone to error and depends on external resources. To me a no-go.
There’s people to use Tasker. Most I know of use WiFi arrival/leave detection but certainly not with G**gle but their own WiFi router. Also many to use owntracks / gpstracker binding, but I’m not sure how to do it in the context of myopenhab.
My favorite is FIND which is included with openHABian but it needs an update. Too much work, too little time these days.
There is a pretty old but nevertheless pretty current thread with a rather complete overview on presence detection solutions here.
I also gave a talk on last but one smarthome day which can be found here.