Hi,
I just got a fit headless DP on a mac mini and it works (kind of) BUT i only get two resolutions to choose from : 4088 x 2304 and 1024 x 768 which is not what i was expecting. How can i enable more resolutions ?

I am running this on a Mac Mini Server Mid 2010 running macOS Sierra.

donnib

The setup involves several components, the graphics hardware, OS driver, monitor and fit-Headless itself.
Fit-Headless contains EDID EEPROM that is programmed with a list of supported resolutions (http://fit-pc.com/wiki/index.php/FAQ:fit-Headless), and just emulates the display enabling the target PC to output the content with its native resolution.
I think the root cause of your case lies somewhere in graphics hardware or the driver.