I feel your pain. I nearly snapped my phone in two of pure frustration. So THIS is how I got my phone back to working :
I use Googlefier to the point where it uninstalls and reinstalls Google Play Services and the errors start. THEN I close it and follow the method this (https://phandroid.com/2020/06/01/how-to-install-google-play-store-huawei-p40-pro/) article from the point where they mention how to remove the errors. The link for DEVICE ID is useless so Google "Device ID Apk". You basically just use the app to see whether the certificate gets removed and put back..
Something extra I did was do the constant Force Close and Delete Data of the Google Service Framework until it was stopped instead of just clearing data as explained in the article.
Googlefier is basically an update of that article but that part of repeatedly opening and closing the play store and installing apps is bullshit. And DON'T delete the Services framework like in that Fonetech video. That's why the play store never opens in the end...
If you are error free, you can upgrade your Google play services to 21.21.16.
(make sure Automatic App updates are turned off in the Play store otherwise your Play services will update and you get errors again). If it happens, force close and uninstall it and install 21.21.16 again. And don't ever delete data on the Play Store again because it will turn on automatic updates again
Hope this helps more people.
PS : I updated the firmware to 126.96.36.199. I think the Android security patches in v223 has something to do with the breakdown on the 11th of October, but I stand corrected