The above may still work, but I now find Frida to work more reliably. No need to push the certificate to the android store, no need to patch the apk.
This link will give you the basics: https://www.bomberbot.com/proxy/unlocking-android-app-traffic-a-practical-guide-with-mitmproxy-and-frida/
A reliable pinning script is: akabe1/frida-multiple-unpinning
use line:
frida --codeshare akabe1/frida-multiple-unpinning -U -f com.microsoft.bing