BPI-M4 Android 8.1 Image : 2020-5-18 update, just support BPI-M4 2GB version
download link:
https://download.banana-pi.dev/d/3ebbfa04265d4dddb81b/?p=%2FImages%2FBPI-M4%2Fandroid8&mode=list
get starting :
http://wiki.banana-pi.org/Getting_Started_with_M4#Install_Android