Log in to Ionic app from a website

I have an Ionic Android app and a Drupal website.

When a user registers in the Ionic app, I make a POST request to Drupal, which sends the user an email to verify the email address. Users have to click the link in the email, which takes them to the Drupal site to set their password.

After users set their password, I would like to show a button in Drupal to open the Ionic app if they have it installed. Is there a way to do that?

I read this tutorial on universal links, but it seems this is about providing a link that can go to an app or a website. What I want to do is link to my app from my website. Any ideas?