Mooneer
Please consider making the Flex Radio AppImage compatible with MultiFlex.
I could help you with the required methodolgy. I have written the necessary MultiFlex code in JavaScript (Node-Red)
If I am not mistaken, you now appear to be using slice A(0) and slice B(1), that are the slice numbers for the first GUI client to contact, and the first two slices to be created. In a single Flex GUI client world, this always works.
For MultiFlex basically you need to find the slice numbers that go with the slice Letter for the desired GUI Client handle number.
You can capture the GUI client name:handle_number, in the sub radio all or when the new GUI client first connects. My thought was to make the value in "client_name" a command line argument as the desired GUI client for FreeDV to bind to and use the appropriate slice numbers for slice A and B.
One new issue would be that FreeDV would either need to be started after Flex and the first GUI client were running, or.....use the Vita49 information packet to detect when a new client is connected and then, bind to the desired GUI client specified in the command line argment....this is what I do in Node-Red.
Alan. WA9WUD