Each cell provider has a way to formulate an email address by combining the phone number and a domain.
Like this:
The trick is you would have to know the cell provider for each of your users. Sending to that special email address goes directly to their SMS.
Then you can share with those users using this method below. It will provide them with a magic link so they can avoid the pin process. Magic Links are pre-authorization one time use links tied to a specific email.
Keep in mind that this will authorize the app with that special SMS email, so that’s the email that will be stored in their user profile.
I should also mention that Magic Links are shared in the pin email as well, if you have it enabled. Normally you can just click on the link instead of entering the pin.