People using Android should live with the notion that Google siphons absolutely everything from their devices. One way is to block any application is not needed to "speak to google" (or Facebook, or any advertisers).
I always use and suggest to other Android users the NoRoot Firewall [1], and then disable/uninstall everything not needed. Of course that applied to IT pros, as tweaking things without the appropriate knowledge may/will result to a phone bricking/reset.
[1]: https://play.google.com/store/apps/details?id=app.greyshirts...
There's no way you could brick the phone by using the NoRoot Firewall.
In general, my problem with these apps is that you shift your trust from one company to another. I have no idea who created this app, what their motives are, how securely they guard their signing key and so on.
There aren’t open source versions?