>I get they need to keep trojans, spyware, adware, etc out of the store
They don't keep out adware. Users have that benefit only when using the iOS app store. There are tons of apps on Android that just wrappers around ad SDKs
You might test out something like Guardian VPN and see just how much stuff your phone is trying to send over the wire without your consent. (Guardian is iOS-only, afaik, but surely there must be Android equivalents.)
Sure, but those are still very far behind software/support wise and you need to be really patient. People who believe in this, like me, have sent them my money, but my daily driver is a modern Android phone which was not only (much) cheaper, but miles ahead in stability and hardware. I send my money and bugreports in the hopes I will have a stable and open phone in my pocket before my death, but there are many years to go as it is.
If we manage to get something like the samsung a31, at a similar pricepoint, with all hardware working before 2025, I would be happy. But I am skeptical when installing yet a newer OS version on my pinephone and start writing bugreports for applications we consider trivial for a daily driver phone.
Edit; being able to performantly and robustly run Android applications in Linux could (sadly but it is a reality) help adoption a lot a well because of proprietary apps (it sucks but I need whatsapp for instance). That is not that close by either I think; anbox is slow and unreliable last I tried.
Nowadays, what's exactly "Adware"? Apps/Games with ads is now usual (remember Opera is called Adware). Possibly an app that forcely displays ads still can be called as Adware, but it's not possible on iOS and need manual additional permission on Android.
They don't keep out adware. Users have that benefit only when using the iOS app store. There are tons of apps on Android that just wrappers around ad SDKs