For those of us who aren't ready to cut the umbilical cord to the mothership, you can also root/firewall on normal android to stop this. In fact I choose to not be able to use banking apps in order to cut out the crappy ads.
It comes with some minor usability issues with captive Wifi portals sometimes, but the trade-off of not having ads in app or while browsing is way worth it IMHO.
It looks like there's an app on F-Droid called "Rethink" that promises to do both firewalling, DNS blocking, and offers a WireGuard VPN. That seems promising, though I must add that I haven't tested it myself.
On the other hand, the functionality is top notch. Easily the best integration of consumer level DNS + firewall blocking in any application on any platform. Just block everything of an application by default and then watch the connection logs for the app and start unblocking stuff via ips, domains or wildcards until the app starts working again.
You can use Google apps and apps depending on them on GrapheneOS via sandboxed Google Play. The vast majority of Android apps can be used. You don't need to stop using Google apps/services or other mainstream apps to use GrapheneOS. It's likely nearly all the apps you use or even all of them work on GrapheneOS. There's a per-app exploit protection compatibility mode toggle (and finer-grained toggles) to work around buggy apps with memory corruption bugs. We avoid turning on features breaking non-buggy apps by default and hardware memory tagging is temporarily opt-in for user installed apps not marked as compatible due to how many memory corruption bugs it finds.
A small number of apps are unavailable due to checking for a Google certified device/OS via the Play Integrity API. These are mostly banking apps, but most banking apps do work on GrapheneOS. There are tap-to-pay implementations which can be used on GrapheneOS in the UK and European Economic Area. Several banking apps recently explicitly added support for GrapheneOS via hardware-based attestation as an alternative to the Play Integrity API. We're pushing for more apps to do this and for regulation disallowing Google from providing an API to app developers for enforcing devices licensing Google Mobile Services. Play Integrity API often portrayed as a security feature but Google chooses not to enforce a security patch level. They're permitting devices with years of missing important privacy and security patches but not a much more private and secure OS. Only their strong integrity level has a patch level check, but the check is only done for recent Android versions and only requires they aren't more than 12 months behind on patches which serves no real purpose.
> you can also root/firewall on normal android
This is different from our Network permission which not only blocks direct access but also indirect access via APIs requiring Android's low-level INTERNET permission. Our Network permission also pretends the network is down through many of the APIs. For example, scheduled jobs set to depend on internet access won't run.