So, basically, it works! With home assistant installed on an rPi3 and the homeassistant plugin I get in Indigo the location of the devices (iPhone); I was not able to get the Apple Watch working, therefore basically for me it is a no-go as you don't always have the iPhone with you when going around the house
I am giving this small piece of HW a new chance, as my wife abandoned the Apple Watch Serie 3 (too old now) and bought a cheap Amazfit GTS 2 Mini. From the spec on ESPresence, all Amazfit shall work flawlessly.