Nextcloud version: 12.0.0
Operating system and version: Nethserver 7 (CentOS-based)
Web Server: Apache 2.4.6
PHP version: 5.6
Replication steps: Go to apps menu
The issue you are facing:
All three categories (Enabled Apps, Disabled Apps, and Your Apps) appear empty (as though there are no apps in each category). In the main admin settings menu, “Error occurred while checking server setup” appears.
Nextcloud log: No server logs, everything is (allegedly) working fine
config.php: https://pastebin.com/2hscuD84