There is this post:
https://community.playfab.com/idea/422/206730217-Link-multiple-mobile-devices-IDs-Android-and-iOS-to-the-same-player.html from Oct, 2016.
If I am reading it right at that time you could link many devices but you could only get one id back via API and dashboard. It sounding like you all where going to change that.
What is the status of this? Is there some page I am not find where I can follow the progress?
Thanks!