Proxy-mode allows the server to accept incoming connections even if you don't have a dedicated IP address or you are behind a complex firewall configuration.
But by default, Proxy-mode works for the SRT protocol.
To enable proxy mode for the RIST protocol, follow these steps in order:
First, click the "RIST Server" button
Then enable proxy mode
If the sequence is followed correctly, the proxy address will start with the rist:// prefix
So you can use this URL for RIST Encoder as endpoint.