I’m not sure how different the interface is on OneUI, but on my Pixel when I swipe up and hold on an app to open the App Switcher, there is a button below the app that takes a screenshot of just that app.

I don’t remember when it was first introduced, but it is a feature of stock Android, so it should be present in some capacity on most Android phones.

You may have tried this already, but Microsoft does have a specific troubleshooter for Windows Hello via the Get Help app and at https://support.microsoft.com/en-us/windows/troubleshoot-problems-with-windows-hello-bf68539e-e95e-48b6-a6cb-455649db3887. Though if all else fails, you could also try uninstalling and then re-installing the “Facial Recognition (Windows Hello)” feature via Settings > Optional Features and see if that helps any or not.