Not all element are "https"

Nextcloud version (eg, 20.0.5): 21
Operating system and version (eg, Ubuntu 20.04): Ubuntu Server 20.04
Apache or nginx version (eg, Apache 2.4.25): replace me
PHP version (eg, 7.4): 7.4.15

The issue you are facing:
Some element of the sites do not redirect to “https” but to “http” which leads to unloaded images or being unable to allow access to web login
Capture d’écran de 2021-02-23 23-08-12

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

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

<?php
$CONFIG = array (
  'htaccess.RewriteBase' => '/',
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'apps_paths' => 
  array (
    0 => 
    array (
      'path' => '/var/www/html/apps',
      'url' => '/apps',
      'writable' => false,
    ),
    1 => 
    array (
      'path' => '/var/www/html/custom_apps',
      'url' => '/custom_apps',
      'writable' => true,
    ),
  ),
  'memcache.locking' => '\\OC\\Memcache\\Redis',
  'redis' => 
  array (
    'host' => 'redis',
    'port' => 6379,
  ),
  'instanceid' => '',
  'passwordsalt' => '',
  'secret' => '',
  'trusted_domains' => 
  array (
    0 => 'aurnytoraink.ddns.net',
  ),
  'datadirectory' => '/var/www/html/data',
  'dbtype' => 'mysql',
  'version' => '21.0.0.18',
  'overwrite.cli.url' => 'https://aurnytoraink.ddns.net',
  'overwritehost' => 'aurnytoraink.ddns.net',
  'overwriteprocol' => 'https',
  'dbname' => 'nextcloud',
  'dbhost' => 'db',
  'dbport' => '',
  'dbtableprefix' => '',
  'mysql.utf8mb4' => true,
  'dbuser' => '',
  'dbpassword' => '',
  'installed' => true,
  'mail_smtpmode' => 'smtp',
  'mail_sendmailmode' => 'smtp',
  'mail_smtpauthtype' => 'LOGIN',
  'maintenance' => false,
  'loglevel' => 2,
  'updater.release.channel' => 'stable',
  'has_rebuilt_cache' => true,
  'twofactor_enforced' => 'false',
  'twofactor_enforced_groups' => 
  array (
  ),
  'twofactor_enforced_excluded_groups' => 
  array (
  ),
  'ldapIgnoreNamingRules' => false,
  'ldapProviderFactory' => 'OCA\\User_LDAP\\LDAPProviderFactory',
  'app_install_overwrite' => 
  array (
    0 => 'tasks',
    1 => 'files_external_gdrive',
    2 => 'occweb',
    3 => 'richdocuments',
    4 => 'richdocumentscode',
  ),
  'preview_max_x' => '2048',
  'preview_max_y' => '2048',
  'jpeg_quality' => '80',
  'theme' => '',
  'mail_smtpauth' => 1,
  'mail_smtpname' => '',
  'mail_smtppassword' => '',
  'mail_smtpsecure' => 'tls',
);

Ok I manage to solve it by executing this command:
occ --no-warnings config:system:set overwriteprotocol --value=https;

PS: I’m not sure if the --no-warnings is usefull but it worked