Hi,

For those interested, but don't read the tracker, i've made a little hack to skip the site course backup (course=1) and a defined list of other courses (replace values "123, 1234, 12345" by id's of courses you want to skip) by adding these lines in backup/util/helper/backup_cron_helper.class.php (line 178 for Moodle 3.5.2, the last 2 existing lines indicate where to put it) :

                // Skip the site homepage course (1) - because it's useless and gigantic with logs
                if ($course->id == 1) {
                    $skipped = 1;
                    $skippedmessage = 'No backup of site home page!';
                }
 
                // Skip courses defined as to be skipped (because Admin knows they're too big)
                // Ideally admin could specify in UI a list of courses to skip - See MDL-60296
                $skipcourses = array(123, 1234, 12345);
                if (in_array($course->id, $skipcourses)) {
                    $skipped = 1;
                    $skippedmessage = 'No backup of this course (defined by Admin)!';
                }
 
                // Check if the course is not scheduled to run right now.
                if (!$shouldrunnow) {