You might want to look into Island/Insular. https://f-droid.org/packages/com.oasisfeng.island.fdroid

Depending on your level of commitment to privacy, this might be a suitable solution for you.

GrapheneOS is certainly on my wishlist too, but Pixels are quite pricey. I guess Rethink is the poor man’s version. Just a per-app firewall.

You should install Rethink and see how much garbage your phone constantly transmits and receives. And this is not even a kernel-level firewall, so who knows how much data Google actually exfiltrates…

I don’t know about a constant audio stream, nor about keywords, but I noticed that Google Keyboard sends out some data every time you type anything. It’s not even that subtle.