Can't update NC17 as Nextcloud Settings claims "Server version 18 or higher is required."

Hi,
I would like to update from 17.0.8 to 17.0.9, but get the following warning:

Updates are missing for these apps
Nextcloud settings

When I look up the Nextcloud Settings App, it tells me:

This app cannot be installed because the following dependencies are not met:
Server version 18 or higher is required.

I am not offered an automatic update to 18.0.9 and I assume this might break the update.
Any ideas?
I have no access to the server, it is merely hosting without SSH access.

Nextcloud version: 17.0.8 - 17.0.8.1
Operating system and version: Linux 5.4.44-2-pve #1 SMP PVE 5.4.44-2 x86_64
Apache or nginx version: Apache/2.4.29 (Ubuntu) (fpm-fcgi)
PHP version (eg, 7.1): 7.2.24-0ubuntu0.18.04.6

Is this the first time you’ve seen this error? YES

The output of your Nextcloud log in Admin > Logging:

Error	PHP	Zend OPcache can't be temporary enabled (it may be only disabled till the end of request) at Unknown#0		2020-09-29T11:12:26+0200
Error	files_antivirus	RuntimeException: The antivirus executable could not be found at /usr/bin/clamscan		2020-09-29T10:40:10+0200
Error	PHP	file_exists(): open_basedir restriction in effect. File(/usr/bin/clamscan) is not within the allowed path(s): (/var/www/clients/client999/web826/web:/var/www/clients/client999/web826/private:/var/www/clients/client999/web826/tmp:/var/www/franzkcloud.de/web:/usr/share/php:/tmp:/usr/share/phpmyadmin:/etc/phpmyadmin:/var/lib/phpmyadmin:/dev/random:/dev/urandom) at /var/www/clients/client999/web826/web/apps/files_antivirus/lib/Scanner/Local.php#42		2020-09-29T10:40:10+0200
Fatal	files_antivirus	OCA\Files_Antivirus\BackgroundJob\BackgroundScanner::run, exception: The antivirus executable could not be found at /usr/bin/clamscan		2020-09-29T10:40:10+0200

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

  'instanceid' => '***',
  'passwordsalt' => '***',
  'secret' => '****',
  'trusted_domains' => 
  array (
    0 => '***',
    1 => '***',
  ),
  'datadirectory' => '/var/www/clients/client999/web826/web/data',
  'dbtype' => 'mysql',
  'version' => '17.0.8.1',
  'overwrite.cli.url' => '***',
  'dbname' => '***',
  'dbhost' => '127.0.0.1',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'mysql.utf8mb4' => true,
  'dbuser' => '***',
  'dbpassword' => '***',
  'installed' => true,
  'updater.release.channel' => 'stable',
  'mail_smtpmode' => 'smtp',
  'mail_smtpauth' => 1,
  'mail_sendmailmode' => 'smtp',
  'mail_smtpauthtype' => 'LOGIN',
  'mail_smtphost' => '***',
  'mail_smtpport' => '465',
  'mail_from_address' => '***',
  'mail_domain' => '***',
  'mail_smtpsecure' => 'ssl',
  'mail_smtpname' => '***',
  'mail_smtppassword' => '***',
  'default_language' => 'de',
  'force_language' => 'de',
  'force_locale' => 'de_DE',
  'defaultapp' => 'files',
  'knowledgebaseenabled' => true,
  'allow_user_to_change_display_name' => true,
  'skeletondirectory' => '',
  'theme' => '',
  'loglevel' => 2,
  'maintenance' => false,
  'app_install_overwrite' => 
  array (
    0 => 'groupfolders',
  ),

The output of your Apache/nginx/system log in /var/log/____:

NA