Warning: printf(): Too few arguments in helpers.php file

Your printf statement awaits additional string argument which would be substituted instead of %s:

    printf(
        // Filters text content and strips out disallowed HTML
        wp_kses(
            __('Read more <span class="u-screen-reader-text">about %s</span>', 'Sema'),
            [
                'span' => [
                    'class' => []
                ]
            ]
        ), "some subject"
    );

This example would produce the following output:

Read more <span class="u-screen-reader-text">about some subject</span>