[SOLVED] Can't access my nextcloud interface and can't find any help in my logs

Nextcloud version (eg, 20.0.5): 22.1.1
Operating system and version (eg, Ubuntu 20.04): Debian 11
Apache or nginx version (eg, Apache 2.4.25): 2.4.51
PHP version (eg, 7.4): 7.4.25

The issue you are facing:

I can’t access anymore my nextcloud interface from any computer of my lan. the thing is that i can’t find anything in the logs.

I got this message :

Internal Server Error

The server encountered an internal error and was unable to complete your request.
Please contact the server administrator if this error reappears multiple times, please include the technical details below in your report.
More details can be found in the server log.

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!):

$CONFIG = array (
  'instanceid' => '',
  'passwordsalt' => '',
  'secret' => '',
  'trusted_domains' => 
  array (
    0 => '',
  'datadirectory' => '/var/www/html/nextcloud/data',
  'dbtype' => 'mysql',
  'version' => '',
  'overwrite.cli.url' => '',
  'dbname' => 'nextcloud_db',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'mysql.utf8mb4' => true,
  'dbuser' => '',
  'dbpassword' => '',
  'installed' => true,
  'log_type' => 'file',
  'logfile' => '/var/log/nextcloud.log',
  'logfilemode' => 0640,
  'loglevel' => 0,
  'logdateformat' => 'F d, Y H:i:s'

Thanks in advance for your help.

Propably an incompatible Nextcloud app is causing the error?

You can try while opening the UI:

tail -f /var/log/apache2/error.log
tail -f /var/log/apache2/access.log
tail -f /<path to your Nextclod data folder>/nextcloud.log | jq

No line were added to the error.log - - [19/Dec/2021:20:22:04 +0100] "GET /nextcloud/index.php/apps/dashboard/ HTTP/1.1" 500 477 "-" "Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Firefox/91.0"

no entry were added to json data.

Thanks for your help !

Start with the easiest check:
systemctl status apache2
It seems, that Apache is not running.

Active: active (running)

Finally decided to erase Nextcloud installation. Topic closed.

Propably FileRun is working better for you?