Kathy - WordPress Theme

Is it possible to use an animated GIF as portfolio featured image? If yes, how?

It is possible, but you would need to override the parent theme’s function and customize it in a child theme.

First, you need a new child theme for the job. Please see here on how to create one: https://uxbarn.ticksy.com/article/8649/

Then in the “functions.php” file of the child theme, add this code:

function kathy_get_portfolio_list_image_size( $layout = 'list', $is_full_width = true ) {
    return 'full';
}

The custom code will override the image size of the parent theme and the GIF file's animation should work.