With plugin

• Install the plugin Easy Fancybox.
• In the settings (in the plugin list), disable all media except iFrames and save.
• Set the iFrame width/height to 95% and 90% (needed for mobile).
• Add fancybox-iframe as a CSS class to menu items or links.

Notes

• Divi buttons: works
• Divi blurb: does not work

Without plugin

Source: https://www.creaweb2b.com/en/open-content-in-popup-without-plugin/