I see some core team on this thread, so just wanted to say THANK YOU! Awesome job! Keep fighting for the users!
I'm totally the wrong person to offer recommendations on mobile, but so far it works very well for me, but then, I use almost no third party apps, and none of them are Play store only. My only complaint is the hardware (outside of their control).
I wish that were true, but if you delete the 100s of binary blobs (many with effectively root access) copied from a stock donor vendor partition the phone won't function at all.
There is no such thing as a fully open source and user controlled Android device today.
I am alright with things that allow for improvement, at least in theory
Sadly this was, to your usual points, at the major expense of security making those devices purely research projects at best and not something anyone should ever actually use.
When you are stuck on a platform that requires closed firmware you are kind of stuck blindly accepting updates from the vendor to patch security bugs, stuck hoping they are not actually introducing new backdoors.
This is why I reject platforms that require closed firmware in the first place to the fullest extent I can.