Dell Optiplex 7020 sff no Display via display port if secure boot in on?

Hi,

when "secure boot" in enabled in Bios (A18) and "Legacy Option Roms" disabled I am not able to have display output via any of the two Display ports. Is this intentional? Video uptput via VGA works ...

I do need Legacy option Roms enabled AND video via Display port.

Any ideas?

Thanks