You won't get the full functionality of the Huawei watch.
You will need to download the Huawei Health App
Now I will say don't bother with the Google Playstore version of the app as it's rubbish.
You will need to download an APK of the app
https://appgallery.cloud.huawei.com/appdl/C10414141This is the one I used when Huawei loaned me the Watch GT3
It worked and gave me full functionality of the Watch
You will need to enable the unknown sources
But personally I didn't get any issues.
You may need to setup a Huawei account. I already have one so I'm not sure there
There is another way, by searching for the Huawei App Gallery and logging in etc. Bit more long winded
You can always ask on the Huawei Community
https://consumer.huawei.com/uk/community/