Glad to hear that you’ve found a solution.
Just FYI you don’t actually need the loop template with Query loop for this.
If the columns option is activated in the customizer, you can just use this snippet to turn it off on the blog/front page:
add_filter( 'generate_blog_columns', function( $columns ) {
if ( is_front_page() && is_home() ) {
return false;
}
return $columns;
} );
Learn how to add PHP: https://docs.generatepress.com/article/adding-php/