There are two remote desktop apps in Google Play Store:
Remote Desktop (latest version: 10.0.10.1129)
Remote Desktop 8 (latest version: 8.1.81.435)
So the one I was using (Remote Desktop 8) does not have a 10.0.8 version.
I've downloaded the other app (Remote Desktop (latest version: 10.0.10.1129)), and it finally solved part of my problem. This app does indeed have a setting for remote microphone, so apparently this was not a bug in the other app, but a missing feature.
Unfortunately this app does not have a touchscreen mode, or so far I haven' found it.
But anyway, problem (partly) solved! Now I'm only waiting for the remote camera redirection feature.
THX!!!!!