We're using the regular TuneIn radio service as the replacement for Internet Radio. Internet Radio as a source in SoundTouch should have already been removed from the list. There is no option to sign into TuneIn Premium or Pro accounts, but this has been passed to development as feedback.
As for it being the core service now is because TuneIn is a fantastic service that not only provides over 100,000 stations around the world, but also offers sports, news, talk, and millions of podcasts all for free! We've supported TuneIn as an integrated service for over a year and our customers have been pleased with it.
The new Smart Home Product line does not support music libraries. We will let the community know if we have any new features for the new Smart Home Speakers.
We are pleased to announce that today, as promised, we are deploying a new custom radio URL streaming feature to the SoundTouch app. This feature will also allow you to set the custom URL as a preset. For additional information please see the Update Release Notes.
Many thanks for all your patience and support as we work to streamline your SoundTouch Internet Radio experience!