Linux Desktop Client can't connect to server

Nextcloud version (eg, 20.0.5): 21.0.2
Operating system and version (eg, Ubuntu 20.04): Debian Buster
Apache or nginx version (eg, Apache 2.4.25): NGinX 1.21.0
PHP version (eg, 7.4): 7.4.18
Desktop-Client: 2.6.2-1build1

I’m trying to get the Desktop Client up and running in order to sync some dirs from my server to the harddisk. But it never successfully connects - the initial connectivity check fails with an error, that $HOSTNAME/status.php times out. But upon opening the very URL in a browser on the same machine, with the same user, returns the status page immediately.
Tried to remove all occurrences of “nextcloud” (‘find . -iname nextcloud’) in my home directory, but this didn’t help at all. Tried to connect through a remote VPN server (in case there’s a problem with my LAN config), but to no avail.

Is this the first time you’ve seen this error? (Y/N): Y

Steps to replicate it:

  1. open Nextcloud client (no profile as of yet)
  2. enter server URL and hit enter
  3. connection timeout.

Any hint greatly appreciated.

The output of your Nextcloud log in Admin > Logging:

none available

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

<?php
$CONFIG = array (
  'instanceid' => 'REDACTED',
  'passwordsalt' => 'REDACTED',
  'secret' => 'REDACTED',
  'trusted_domains' => 
  array (
    0 => 'REDACTED',
    1 => 'REDACTED',
    2 => '192.168.178.*',
    3 => 'REDACTED',
  ),
  'datadirectory' => 'REDACTED',
  'dbtype' => 'mysql',
  'version' => '21.0.2.1',
  'overwrite.cli.url' => 'http://localhost',
  'dbname' => 'nextcloud',
  'dbhost' => 'localhost:/var/run/mysqld/mysqld.sock',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'mysql.utf8mb4' => true,
  'dbuser' => 'REDACTED',
  'dbpassword' => 'REDACTED',
  'installed' => true,
  'activity_expire_days' => 14,
  'auth.bruteforce.protection.enabled' => true,
  'blacklisted_files' => 
  array (
    0 => '.htaccess',
    1 => 'Thumbs.db',
    2 => 'thumbs.db',
  ),
  'cron_log' => true,
  'enable_previews' => true,
  'enabledPreviewProviders' => 
  array (
    0 => 'OC\\Preview\\PNG',
    1 => 'OC\\Preview\\JPEG',
    2 => 'OC\\Preview\\GIF',
    3 => 'OC\\Preview\\BMP',
    4 => 'OC\\Preview\\XBitmap',
    5 => 'OC\\Preview\\Movie',
    6 => 'OC\\Preview\\PDF',
    7 => 'OC\\Preview\\MP3',
    8 => 'OC\\Preview\\TXT',
    9 => 'OC\\Preview\\MarkDown',
  ),
  'filesystem_check_changes' => 0,
  'filelocking.enabled' => 'true',
  'htaccess.RewriteBase' => '/',
  'integrity.check.disabled' => false,
  'knowledgebaseenabled' => false,
  'logfile' => 'REDACTED',
  'loglevel' => 0,
  'logtimezone' => 'Europe/Berlin',
  'log_rotate_size' => 104857600,
  'maintenance' => false,
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'memcache.distributed' => '\\OC\\Memcache\\Redis',
  'memcache.locking' => '\\OC\\Memcache\\Redis',
  'overwriteprotocol' => 'https',
  'preview_max_x' => 1024,
  'preview_max_y' => 768,
  'preview_max_scale_factor' => 1,
  'redis' => 
  array (
    'host' => '/var/run/redis/redis-server.sock',
    'port' => 0,
    'timeout' => 0.0,
  ),
  'quota_include_external_storage' => false,
  'share_folder' => '/Shares',
  'skeletondirectory' => '',
  'theme' => '',
  'trashbin_retention_obligation' => 'auto, 7',
  'updater.release.channel' => 'beta',
  'mail_smtpmode' => 'sendmail',
  'mail_sendmailmode' => 'pipe',
  'mail_from_address' => 'nextcloud',
  'mail_domain' => 'REDACTED',
  'mail_smtpauthtype' => 'LOGIN',
  'mail_smtpauth' => 1,
  'mail_smtphost' => 'REDACTED',
  'mail_smtpport' => '587',
  'mail_smtpname' => 'REDACTED',
  'mail_smtppassword' => 'REDACTED',
  'mail_smtpsecure' => 'tls',
  'default_phone_region' => 'DE',
  'app_install_overwrite' => 
  array (
    0 => 'dicomviewer',
    1 => 'files_mindmap',
    2 => 'carnet',
    3 => 'onlyoffice',
    4 => 'richdocuments',
    5 => 'richdocumentscode',
    6 => 'documentserver_community',
    7 => 'files_photospheres',
    8 => 'telephoneprovider',
  ),
  'has_rebuilt_cache' => true,
);

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

no log entries generated - looks like the client never gets its request out to the server