I should mention that DuckDuckGo recently released an android browser and it is privacy focused. I cant tell you how well it does its job BUT the important thing is that it has an experimental feature that creates a virtual network interface that routes coms and blocks phone home attempts and tells you what app is doing what.
I have had it running for a few months and its crazy to see how much traffic is going on without your knowledge.
Ive only started looking into these. GrapheneOS looks cool, but being stuck with only the Pixel is kinda annoying and google is being shitty about supporting it. Removing drivers and squashing git commits, making it harder to support.
I need to look at the others to see how they fair.