Any experience with Two-Factor Gateway app using as messenger?

I am interested in potentially changing from the TOTP offical app to the Two-Factor Gateway app using WebSMS to send the authentication code to my users. Reason is that it does not allow a grace login for users to set up two-factor authentication. Seems using SMS should resolve this problem as I can add a user’s phone number when I create the user account (even if I have to log into their new account first to add it).

Does anybody have experience they can share about how well this app is working? Any problems encountered? Thank you