Question DisplayPort audio not working

Jun 27, 2021
i've always used an hdmi cable to connect my pc to the monitor (Samsung C24RG50FQU), and i have speakers connected to the monitor via jack. i've done this because the pc is not the only device connected to the monitor.
now i had to change the connection to a displayport 1.2 cable (this one) but even if the monitor is recognized as an audio output, there's no sound coming out from the speakers.
i tried using some headphones instead of the speakers but the problem persist.
i have this problem on both windows 10 and ubuntu 20.04, and i also tried using ubuntu live from an usb stick (so that i had no custom pc settings saved) but nothing.
in windows 10, in the control panel, i can actually see the audio coming out of the monitor but in fact it doesn't work.
i have a gtx 1660 and i also tried to connect the dp cable to all the other ports (3 dp ports and 1 hdmi)

in the monitor settings i can choose the displayport version from 1.1 to 1.2+, but none of these resolve the problem.

i already tried all the "set this device as default" etc, that's not the problem.

the monitor output, at least in ubuntu, is recognized as hdmi / displayport 2 - tu116 high definition audio controller.