Hi all, just to close this on my end.
Dell Optiplex 7040 Micro worked fine with video and HDMI audio after a few attempts.
The setup:
7040M is based on Q170 chipset, (which is why I, my attempt to use configs from Optiplex 3040M did not go that fine.)
i7-6700T / HD530 / 16Gb
Using HDMI to LG...