Eury Now I know exactly which services to block/turn off in Google Play Services and Google Messages using App Manager/Servicely! Thanks so much for that!
I get that not everyone has the ability though... I only do because I compiled GrapheneOS from source, installed a hosts file with 1.5 million lines, and I compiled one kernel with KernelSU and one without, and one with Magisk, all with the same keys. I can sideload one OTA update, give myself root permissions, then quickly do a backup or restore, or mess with app services, receivers, providers etc., then sideload another OTA to revoke the ability to grant root and all current root permissions. KernelSU also allows giving root out on the "principle of least privilege," so you dont even need to ever give full root to an app, just the exact root permission it needs for the task!
I started to use Google Messages because of the upcoming thing about Apple integrating RCS, and my whole family owns iPhones. I really want to be able to get away from SMS, and use E2E messaging. But at what cost? Hopefully nonebor a low one, but as this paper shows, apparently a large cost in privacy unless something is done!
Tl/DR: go to https://grapheneos.org/build/ and make your own build for the best of everything, and turn off those trackers. Then you can use apps like Google Messages and not worry about the tracking and inter-app communication!