works
- Macbook → USB C/ DP → monitor
- Macbook → thunderolt dock → USB C/DP → KVM → DP/DP → monitor
- Macbook → thunderbolt dock → miniDP/DP → KVM → DP/HDMI → monitor
- macbook → thunderbolt dock → USB C/HDMI → HDMI/HDMI → monitor
does not work
- Macbook → thunderbolt dock → USB C/DP → KVM → DP/HDMI → monitor
- Macbook → USB C/DP → KVM → DP/HDMI → monitor
this is the only setup that works. Switch any single cable and it doesn't.
Note also that DP++ is not available on DisplayPort Alternate Mode over USB-C (as is used on many current compact devices like smartphones and notebooks). So if you use USB-C you will always need an active adapter to connect to an HDMI display.