Indeed ASIO in only for Windows.
Actually you havethe6 channels opened. The "Audio Analysis Channels" you can select from preferences are the one used for beat detection / general waveform and spectrum used in Materials. You should see al channels there, as in following screenshot:
But you can use all the channels for controlling parameters:
- Right click on a widget and choose "Add Control / Audio"
- In Controls List, select your audio control, press the "Channel" list button and you'll see all available channels.
If you can only see channels 1 & 2, please send a screenshot of preferences / audio tab