I finally figured out a solution! Maybe this works for you as well.

-PROBLEM-

I ran into the same issue of not having any device input detected:

1. Downloaded and installed the HoloLens Emulator 2 (10.0.20348.1535)
2. Started the program > Booted up fine
3. Simulation Panel does not open, and no input is detected.

-SOLUTION-

1. Go to Settings > Update & Security > For developers
2. Enable Developer Mode

Afterward, starting the emulator fixed the problem for me. Mouse input was recognized, and I could open the simulation panel through F7 or the UI.