How to disable all featured images using "App" from the Site Library.

Hello,

I activated the Site Library module, then chose the "App" layout from the library.

I want to disable displaying the feature image at the top of the post/page for all posts/pages. I saw in the forum where I could go to "Customize -> Layout -> Blog", then disable the featured image. However, I only see a "Content Type" selection box. (Image: https://imgur.com/a/B2cMihn )

Is there another way to disable displaying the feature images? (I'm happy to edit the functions.php file or anything else.)

All the best,

Jason