Olympus OMD E-M1 Mark III seems to have clean HDMI output.
Video dataBased just the specs.
Video output resolutions: 1920x1080
Video output ports: HDMI?
Lens mount: Micro Four Thirds.
Crop factor: 2 in respect to a 35mm film. More crop factor means the sensor is smaller.
This camera uses the Micro Four Thirds mount to attach lenses to it, and there are a lot of cameras using the same lens mount.
Search cameras with the Micro Four Thirds mount.
What is clean HDMI
Clean HDMI output means that a camera is able to output a live video signal through HDMI without any graphics, marks, data, autofocus regions or any other thing that usually shows on the camera display.
The clean HDMI output only includes just the video, nothing more, so it can then be sent without any visual distractions to any other live video equipment (HDMI capture card, professional video switcher) for live video streaming or broadcasting.