@oldbutndy said:
I also found a human discussion that said major US carriers tried implementing their own versions, then gave up & let Google support it.
It happened here in France also... Some used a dedicated application, while other implemented it natively on devices supporting it back in time.
All finally stopped and chose the "easy" google way...
Edit : it appears that Deutsch telecom was part of this
https://fr.wikipedia.org/wiki/Joyn