Meta/Facebook preinstalls an app called Meta Services (previously Facebook services) on a very large percentage of android devices (I’ve never used one without it) and while they claim it helps updates and synchronisation between different meta apps, it is very suspicious. Why preinstall it on devices of people who will potentialy never use a single meta app?
Go to your app list/app management and show system apps and find anything with the words “meta” or “Facebook” then turn off network access for those apps (if you can) and disable them. (eg. Meta app manager, Meta app installer).
https://www.askwoody.com/forums/topic/meta-services-an-android-app-or-not/
https://fixyourandroid.com/about/facebook-app-manager/
https://www.reddit.com/r/GalaxyS20FE/comments/ttmx4t/meta_services/
Edit: Looking around I have found several people complaining that this app is using their ram for 10 hours a day even though they don’t use anything Meta. That’s even more suspicious.
Not the person you asked, but I run Calyx. It has microG services to impersonate google services. It works most of the time, but I have found a few apps that straight up don’t work since microG isn’t 100% viable yet.
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If you use the aurora store it will tell you what apps require google services. My banking app works perfectly fine though I’ve heard others don’t so your milage may vary. Calyx came preinstalled with an email app which works fine, though f-droid has dozens of foss alternatives. Calyx also came preinstalled with chromium though I switched to fennec (firefox). I believe whatsapp works though I don’t have it installed nor will I.
Oh, i forgot the first part. Mostly the ones I’ve tested that don’t work are like quality games, chronotrigger and kotor come to mind