I have a VM on our LAN with Ubuntu 20.04 and Zammad Community installed and working. We use Synology Application Portal (Reverse-Proxy using nginx) to access it from outside and this is working too.
But a functionnality of Zammad is Livechat and uses Websockets to work and, that's the snag, Websockets doesn't work, Chat will not initialize on our main website (hosted outside).
Here is the error in javascript console on the website while loading the livechat :
The solution is to enable Websocket communication on the Synology Application Portal entry by adding some custom headers.
In the DSM, open the Control Panel under "Application Portal" tab
Select the app you want to enable Websockets
Go to "Custom Headers" tab
Add theese two entries:
"Upgrade" with value "$http_upgrade"
"Connection" with value "$connection_upgrade"