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Nextcloud version: 16.0.3.0
Operating system and version: Fedora 31
Apache or nginx version: Apache/2.4.41 (Fedora)
PHP version: PHP 7.3.13
The issue you are facing:
When attempting to follow this guide to set up LDAP with FreeIPA, when modifying my User filter, the “groups” drop-down is greyed out. I’ve spotted a few other support articles and bug trackers like this one which suggest that the “memberOf” LDAP directive is responsible. In fact, when I manually enter an ldapUserFilter of (memberOf=cn=nextcloudusers,cn=groups,cn=accounts,dc=homelab,dc=local), Nextcloud freezes up and I see a “Gateway Timeout” after a while.
The funny part is, I’ve had a different instance of Nextcloud working with FreeIPA in the past. I set it up using the linked guide, too. But before I wiped my hard drives, I forgot to save my configs and stuff for Nextcloud. 
I know that “memberOf” should work, because it’s worked in a different instance. I don’t understand why Nextcloud now freezes when I try to manually specify it.
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 (
'instanceid' => '*',
'passwordsalt' => '*',
'secret' => '*',
'trusted_domains' =>
array (
0 => 'dragoncloud.homelab.local',
),
'datadirectory' => '/var/www/nextcloud/data',
'dbtype' => 'mysql',
'version' => '16.0.3.0',
'overwrite.cli.url' => 'https://dragoncloud.homelab.local',
'dbname' => 'nextcloud',
'dbhost' => 'dragondb.homelab.local',
'dbport' => '',
'dbtableprefix' => 'oc_',
'mysql.utf8mb4' => true,
'dbuser' => 'nextcloudusr',
'dbpassword' => '*',
'installed' => true,
'ldapIgnoreNamingRules' => false,
'ldapProviderFactory' => 'OCA\\User_LDAP\\LDAPProviderFactory',
'log_type' => 'syslog',
'memcache.local' => '\OC\Memcache\APCu',
);