found 988323 0.11.2-2 thanks
That's the default in upstream, too. See https://github.com/roundcube/roundcubemail/blob/master/config/defaults.inc.php:
$config['log_file_ext'] = '.log'; In Debian, this changed either in buster or bullseye.(One need to set backend = pyinotify or similar too, but that's a different issue.)
