Oxygen's Image component does not provide the option to insert an Image-type custom field's Alt text using the dynamic data.
This members-only tutorial shows how we can create a custom PHP function that returns the Alt text and add it to the image's HTML output.
Before:
After:
Step 1
Ensure that your Image field's Return Format is set to Image Array in your ACF field group.
Step 2
Install and activate Code Snippets plugin.
Go to Snippets > Add New.
Title: [Function] Get ACF Image Alt Text
Code: