Nova is still my primary.
I just disable all its network and data permissions. It all still works just fine, and doesn't have any way to send any data home.
I've tried most all the others, and always come back to Nova
That disable the app itself from accessing the internet, but it does not forbid it from tunneling it's network access through other apps.
I don't remember the article, but I remember that I read years ago that a group of apps were tunneling their network activity through Facebook app and YouTube.
If I remember the article , I will post the link here.