[Huawei Mate XS Questions & Answers] Cyriuz:
I can try to summarize the steps I think is needed after trying for a couple of days.

(Disclaimer: I haven't actually tried it from scratch but I'm pretty sure these are the only things needed)

(Start at 10. if you already have it working but want to get rid of the errors.)

First get the files from these videos:

https://www.youtube.com/watch?v=3MfxLUNWJr0

https://www.youtube.com/watch?v=sEBrOwQP_0o

1. Put the files on a USB stick (Dunno if it is needed, it might be fine to put them on the phone directly)

- (!)The Huawei folder needs to be in the root.

- You'll have 4 important folders, Huawei, Google pack, fix and newfix.

2. Go to Settings/System & updates/Backup & restore/Data backup/External storage/USB storage/17 October 2019 and then press restore.

- Enter the password it asks for (a0000000)

- This will put 2 sketchy apps on your homescreen.

3. Install all apks in the Google pack folder.

4. Run the sketchy app with a purple G and press Activate when it asks you to. Then continue pressing the buttons (really see the video for this) and restart the phone when it fails with the first spinny thing.

- Once restarted you will be spammed with errors, ignore these for now (disable sound, they are super annoying)

5. Revoke the access and uninstall the sketchy apps. It's not needed but I wouldn't leave it enabled for a second longer than I need.

- Go to Settings/Security/More settings/Device administrators and set the G app to inactive.

- Uninstall the G app and the other one as well I assume.

6. Uninstall Google Services Framework.

- Settings/Apps/Apps - search for google and enable Show system processes in the right corner menu.

- I had issues with this on my phone that it would just freeze and restart when I tried it, the solution seemed to be to clear all its data and force stop the proccess until the force stop button stopped being active.

7. Go to the fix folder and install

google account manager4.0.3.apk

8. Create your google sync accounts in Settings/Users & accounts/Add an account/Google.

- Follow the instructions as you would for logging in to google.

- (!) Add all the accounts you want to sync now, I can't seem to add them afterwards.

9. Go to the fix folder and install

com.google.android.gsf_10-29_minAPI29(nodpi)_apkmirror.com.apk

- Restart and after that everything should work except for a lot of errors everywhere. At this point the fist video tells you to just disable the notifications but it doesn't help for example gmail and you have to do it for every new app you install so it is pretty annoying. The google sync also broke for me after restart.

10. Install the Device ID app from the app store (https://play.google.com/store/apps/details?id=vtechnotm.com.deviceid&hl=en)

11. Uninstall Google Play services - same procedure as 6.

- To verify that you're on the right path the version you just uninstalled should have been version 19.2.75.

12. From the newfix folder install

modagain1gsm.apk

.

- This is the Google Play services version 19.4.20.

- Make sure the play store still opens, it might show an error but should preferably still show apps.

13. Reinstall Google Services Framework.

- First repeat step 6.

- Install the file in newfix

Google Services Framework-com.google.android.gsf-29-v10.apk

14. Start the Device ID app and verify that you don't have any GSF ID.

15. Poke around in the play store until the Device ID shows a GFS ID, see the video.

- This step feels very unscientific and sometimes it took me forever...

- If it doesn't work make sure you have Google Play services version 19.4.20 installed.

- Don't reboot your phone, it should regenerate the ID just by poking around. I got it regenerated when rebooting but then it didn't work after that.

16. You got the ID generated! Uninstall Google Play services and install the file

com.google.android.gms2.apk

from the newfix folder.

- Verify that Google Play services is now version 20.12.14.

That's it! Everything should work after this.

I'm pretty confident you can skip some steps here, for example you could install Play services 19.4.20 from the newfix folder already at step 3 to avoid having to reinstall once. But I'm also super unsure why all this actually works so I'm scared to change the procedure :)

Feel free to suggest corrections!