MiniDisplay port to HDMI to optical 5.1 audio only has 2-channel output

I have a Macbook Air 2017. My goal is to have an optical output capable of 5.1 audio for my home theatre. My series of connections are, mini display port to hdmi and the hdmi connected towards hdmi to optical output and optical connected to my 5.1 home theatre. My midi setup and audio out setting automatically detected the hdmi out and and the hdmi icon appeared in both settings. But in my midi setup, it is showing 8 channels but, volume level of all of them is shown as disabled. All of the channel volume sliders are disabled. When I go for configuring, it shows 5.1 out. But when I tried to test each channels, only left and right are heard. All other channels are silent. When I played a 6 channel audio, it is missing every surround except from left & right. **I tried everything like soundflower, soundflowerbed app, MonitorControl etc. Nothing worked, still hearing only 2 channels.** **Is there any solution for this? I need a 6 channel audio output.**