@devvv4ever thank you so much for your help and comments. I am somewhat technically competent but this is so very complicated. How will average user ever know. I think Google rigs this on purpose to make it difficult outside of their ecosystem.
Of course… They don’t want people to store data outside their servers… Data is their business 😉 We try to make it very easy for users (auto-detection of resources, integration with Android storages, etc) - but I admit that there are more difficulties of course if the sync is not 100% inside the Android software. However the manufacturers own battery saving features are the biggest step for users from our experience, and this causes the most of support time.