“Third party Siri support requires iOS 10 or later and it requires installing the third party apps which you wish to use and which have Siri support,” OS X Daily writes. “Other than that, you’ll have to manually enable Siri support for the third party apps.”
“Something worth noting is that only the most major apps at the moment have Siri support, and it’s not unusual for you to have many apps on your iPhone or iPad but only have a small handful with Siri support,” OS X Daily writes. “Over time the amount of apps which support Siri will likely expand, but for now it’s a relatively small subset of apps from usually the biggest players.”
How to enable Apple’s Siri for third party apps in iOS 10 here.
MacDailyNews Take: Siri on third-party apps work great. We use Siri all the time with the Nike+ Run Club app on our Apple Watches, among others.