Trying to link to a php template file but its blank

Question

From this Stack Overflow qestion It shows a bunch of ways to make page templates. But I don't want to use a page template that uses Gutenberg. Is there another way to make a PHP file like a tos.php, and link to it by <?php echo get_template_directory_uri() . '/tos.php'; ?> I tried to link the page that way but gives be a blank page.

    <?php 
    /* Template Name: ghfjghjg*/

    get_header();
    ?>

    <main id="primary" class="site-main main-header">
        Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor    incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

    </main><!-- #main -->

    <?php
    get_footer();

Also tried, adding this to my functions.php.

function include_TOS() {
    return  __DIR__ . 'tos.php';

}
apply_filters( 'template_include', 'include_TOS' );

Answer 1

get_header() and get_footer() are WordPress functions, not native PHP. If the code snippet you've posted is the entire content of tos.php, you're not loading WordPress at all, the functions don't exist, and so tos.php is throwing a fatal error. It's likely that your web host is configured to not display fatal errors, so you see an entirely blank page.

Further: Gutenberg is an editor, and shouldn't affect the display of pages on the front end. If you're trying to specify that a given post or page should use your tos.php template, you should have a look at the template_include filter.