The Microsoft Authenticator app cannot add accounts directly from URLs using the otpauth URL schema. All otpauth:// links are intercepted by Google Authenticator only, this prevents the user from adding his accounts from third party sites directly with the
click of a button in the mobile browser.
Check out https://authenticator.ppl.family/ to see the links in action. As you can see, the link will be opened with Google Authenticator only.
Please update the app accordingly so we can use the Microsoft Authenticator app to add accounts directly, thank you. Also remember to update the Windows Phone app as well, don't just abandon the UWP platform because it is still widely used.