I am planning to buy a rpi 3 for Android. It needs to use the built-in Bluetooth. I am wondering how stable the current Android ports are, especially for Bluetooth support? Which OS version is currently ported?
After four years , Android for any Raspberry Pi model is still in beta state. You can follow the progress of the community porting efforts here.
After 2012 , the foundation took the stance that they see little benefit in supporting Android , as they now percieve it as mainly encouraging consumption instead of creation.