In Sharepoint 2019, I created a contact page with a phone number and email address. I edited the source page and added the following html tags since I wanted the email and phone number to be clickable:
<a href="mailto:contact@gmail.com">contact@gmail.com</a>
</br>
<a href="tel:123456789">123456789</a>
- mailto is working and open default mail application.
- However, tel is not working and cannot be clicked.
This HTML code works as tested on an HTML page.