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.
And now you're running a two year old phone and it's effectively obsolete.
If they would just upstream their firmware into the Linux kernel, you could upgrade these phones for years and years. Until the hardware is actually physically incapable of running the latest features.
Some vendors, like Google, promise to provide updates for a long time. But it's just that - a promise. There's no technical guarantee or mechanism for this, it's purely based on trust.