I don't think AVI allows 2 audio tracks. Does it?
It does! Multiple audio/video/subtitle tracks in AVI are possible (
AVI-mux GUI) and VLC can handle it very well.
When opening file, just tick
[v] Show more options
Add "
:audio-track=1" in Edit Options input field, for example:
Edit Options [ :file-caching=300 :audio-track=1]
You can handle all tracks at the same time if you use "
:sout-all" instead.
You can try to
remux (MKV to AVI) without reencoding of video and audio tracks. Just create and select new transcoding profile there (Encapsulation: (o) AVI; Video codec: [v] Video, [v] Keep original video track; Audio codec: [v] Audio, [v] Keep original audio track).
You can also use
Media > Stream instead of Media > Convert/Save and you will see "Generated stream output string" at the end of the configuration process where you can do another adjustment (advanced options) if you need.