@devvv4ever I’d love to disable the sync per-account as you suggest, but this workflow seems to be inavailable on any of the Androids (6.0,7.1,8.1) I have here for testing, as long as the global sync is off, which is the state I have to start from…
As far as I observed, when global sync is on, the toggle button for the per-data-source setting is there, fine; then I can control the auto sync state of each item. But as soon as I switch off global sync, the toggle button is gone.
So I’d have to trust Google to do act privacy friendly, giving me a chance to see in advance what will happen when I turn it on - this is where I am pessimistic, based on a test I just did: In globalsync=off situation, the status note “sync OFF” under each single item just repeats the global state - it does not reflect the state it will take when I switch on global sync. I tested this only on LineageOS (which has no google apps/libs to leak anything to), would be interested to know if same applies to stock Androids. So without any such information I have no way to see if data will be “shared to Google” or stays mine. The whole UI design of the account settings looks like a Google data trap to me. Fits the business model.
Obviously, if I could be sure I have done the per-account blocking back in the factory reset state, I could savely switch globalsync on now. Unfortunately, I did not do that, as other apps like messengers don’t need this and thus globalsync=off sounded like the better thing.
Being aware that this is not DAVx5 specific but a generic issue in Android user “guidance” concept, I admitted before that likely I am just failing to find the right tutorial to offer a simpler way to go. Maybe it is enough to “only” remove all data providers now (hoping that this actually cleans all caches), flip the global switch, assert in the google account that the evil empire is off, and then re-install the adapters for my data.
I will adress this question in a broader generic forum/context.