simogana96
What do you mean by "also create a compose.json files"?? You simply download a plugin, upload it to your include/plugins/ folder, and then install it via the UI.
Error 500 is generic and hints at deeper issues that should be logged elsewhere. You should check all possible logs (general server logs, webserver error logs, PHP error logs, MySQL/MariaDB error logs, osTicket System Logs, Browser Console logs, etc.) for related errors.
Cheers.