Hello Rick,
I have used this site three times with no issues at all. I was given the info about the apk site from another member.
Here is the apkmirror website I used.
You searched for DJI Go - APKMirror
Back when Go4 ver.4.0.5 came out I upgraded my Huawei Raven phone. I started getting "No Signal" during flight and kept crashing so I downgraded back to ver.4.0.4 (variant #1021523) that is listed on the apkmirror website. When Ver.4.0.6 came out I decided to give it a go. During 2nd flight the app crashed and I had a black screen. I activated RTH and thankfully my drone came back home and landed. Needless to say I deleted all DJI files and uninstalled the app. Restarted my phone and downloaded Go4 ver.4.0.4 again off the apkmirror website. Everything back to normal. I have also loaded and use the older GO3 app ver.3.1.3 on my Sam Tab A6 and runs flawless. Although it always says DJI no longer supports the app for Mavic Pro, it works great.
Oh... I also downgraded the firmware back to .550 using DJI Assistant2.