There’s no such option in GP out of box, unfortuanly.
But we can try this workaround by inserting a GenerateBlocks container with the dynamic background image (featured image) to the
1. Go to appearance > elements, and create a new block element, choose
hook as the element type, and choose
wp_body_open as hook name, choose location according to your needs.
2. Add a container block of GenerateBlocks, set the dynamic image background:
3. Add a CSS class to the container block, eg.
4. Add this CSS to customizer > additional CSS: