Atpresent there is no such way to control the layout of learndash courses page.
So can you pls try add the below code in framework/presentation/layout-manager.php file in function get_current_layout()
elseif (is_page_template('template-ld-courses.php')){
$default_layout = '1c';
$layout = $this->get_layout_option_value('mo_course_layout', $default_layout);
}
Then you can manage the layout through themeoptions > Site layout .
Instead of making direct change in the theme file pls override the function get_current_layout in invent child theme . So that you can preserve the change even after theme update.