Sending RTMP streams directly to Loola isn't supported yet.
However, if you are on Windows, there's an easy workaround for accepting RTMP streams with the help of ManyCam.
The flow is: RTMP --> ManyCam --> Loola --> Social Platforms
Here's how to set an RTMP ingest server using ManyCam:
Start by creating a new RTMP server:
Next, use your streaming software to send the RTMP to your local RTMP server, here's an example from OBS:
After successfully adding the RTMP source in ManyCam, simply select ManyCam as a source in Loola: