I managed to get this all working by invoking a full interactive editor session and running a startup Python script that looks for a render config file to see if any rendering should be performed. In the finished callback for the queue, I use unreal.SystemLibrary.execute_console_command(None, “QUIT_EDITOR”) to close the editor.
Am I missing anything? It seems this is the only way to get Movie Render Graph working with Python automation, as the Python-based runtime Executor only works with -game and MRG isn’t supported in -game, while running via -ExecutePythonScript has the aforementioned problem of shutting down immediately and not waiting for any callbacks. Ultimately it would be more convenient if I could pass arguments directly to the script with -ExecutePythonScript instead of reading a config file from disk, but this works for now.
Thanks for any input!