Divi's Dynamic Content feature is great for enhancing your post / page templates with post-specific information. While Divi includes an option to show the Post Created Date using Dynamic Content, there is no equivalent option for the Post Updated Date. If you'd like to add the Post Updated Date via Divi's dynamic content feature, here's how to do it:

Add a Post Updated Date option to Divi's Dynamic Content using Divi Dynamic Content Extended

Divi Dynamic Content Extended enhances Divi's dynamic content with a variety of new features, including adding a "Post Updated Date" option to the dynamic content menu. You can use it as follows:

Open the settings for the module you wish to add the post last modified date to.

Locate the setting you want to add it to, and hover over it to reveal the dynamic content icon.

 Click on the dynamic content icon.

The dynamic content menu should now appear, with the Post Updated Date available as one of the options. Click on this option to select it.

 You should now see that your field has been set to take the value of the post's last updated date.

If you'd like to add text before or after the date, you can do so by opening the dynamic content field's settings:

 Enter your desired text and then save the dynamic content settings.

 Save the module settings.

Save the post / page to confirm your changes.

Now view your page on the front-end.

You should now see the post's last modified date displayed on the module, e.g.: