We'll create fresh WordPress site with AMP Img Shortcode installed. You have 20 minutes to test the plugin after that site we'll be deleted.
This plugin from WPZA provides your website with a shortcode to display AMP images, rather than using the standard HTML img tags in WordPress.
To insert the image, you must use the image attribute as such: [amp-img image="https://wpza.net/example-image.jpg"]
To insert the alt text, you must use the alt attribute as such: [amp-img image="https://wpza.net/example-image.jpg" alt="Example image alt text"]