I gave up on Ethos when they orphaned my Horus X10S-E. But in general terms, the first 8 channels can be linked to sticks/knobs/sliders, or switches. If you use a Frsky wireless dongle (btw - if your TX can do the old ACCST/D16 to bind to it), you can get 8 more channels - but Windows (and Real Flight therefore) insist on seeing them as button presses. So it can be interesting to get Switch A↑ to look like a joystick button 1 press, while A↓ is button 2 press...etc. Can be done, but it takes some work to figure out.
It does present a "joystick mode" selection when you plug in a cable, but if it is similar to how OpenTX or EdgeTX do it, you only get the first 8 channels as outputs to the computer.
With EdgeTX one can bypass that corded 8 channel limit by selecting Joystick configuration in the Model settings instead of using the start up prompt - I have 18 channels useable for Microsoft Flight Simulator controls, and there is the availability to do more. But in a quick check of the current manual, it doesn't look like that has been implemented in Ethos.