Unfortunately going from iOS to Android is out of the frying pan into the fire. Android is much worse from a privacy point of view. You can easily see this by just spying on network traffic and DNS requests from the device. It's constantly telling everyone about you.
Your choice in mobile is walled castle or forest full of thieves.
I suppose there are open source phones around but I don't personally find them that useful yet. The main things I want to do with a mobile device is interact with services like Uber, Lyft, Netflix, etc., and get directions. I suppose directions exist via OpenStreetMap but can you reserve an Uber on a Linux phone?