Here is the latest statement from Phonak on the iPhone XS/XS Max issue:
Marvel Phone Compatibility – great news for iPhone X users!
Hopefully, you and your patients have taken advantage of our new support site marvel-support.phonak.com. Here you’ll find information on phone compatibility as well as how-to videos on setup and FAQs. We have received some feedback from you on the iPhone X models, and our additional testing showed these phones to have intermittent Bluetooth® connectivity with many devices, including Marvel hearing aids.We have collaborated with Apple and have identified a solution to Apple’s connectivity issue via a firmware upgrade to our Marvel hearing aids. This firmware will be available in the new version of Target coming next month with the release of our Audéo™ M 312T and 13T models. So reassure iPhone X users that in just a few weeks they’ll be able to stream phone calls, music and more without issues!