Add a note about multi-display limitation
Secondary display mirroring is read-only before Android 10.
@@ -396,6 +396,10 @@ The list of display ids can be retrieved by:
adb shell dumpsys display # search "mDisplayId=" in the output
```
+The secondary display may only be controlled if the device runs at least Android
+10 (otherwise it is mirrored in read-only).
+
+
#### Turn screen off
It is possible to turn the device screen off while mirroring on start with a
