The problem with GrapheneOS as a way to protest what Google is doing with Android is that you have to buy a Google Android device to be able to use it. Buying a Google device to be able to protest what Google is doing with their Google devices seems counter productive.

I don't know how good /e/OS is, but at least there is a place to get it factory loaded on cell phones and install it on phone brands other than Google.

And then there is Lineage OS, which I've had good luck using the extend the life of phones in the past. I haven't tried it since Play Integrity started being such an important feature, but I suppose that just pushes one to be even more open source on their Lineage device. I've been wanting to try Lineage again, but I misplaced the phone I want to try it on.