PHP errors not printing to the log

Hi – I created a Hetzner VPS with the WordPress image and put a handful of WordPress sites up. I have get the PHP error log to display on the screen, but I can’t get it to record anything to wp-content/debug.log. Presumably I’m doing something with wp-config.php incorrectly OR maybe there’s something with Hetzner servers? It’s a LAMP stack on there. Where would a setting or something be aside from wp-config that would control this?