Two external monitors with USB hub not working

Hi,

I have two external monitors connected to my steam deck with a usb c hub. Both monitors are connected with HDMI.

The problem is that both monitors are mirrored and show the same content. But when I enter the display configurations in desktop mode, there is only one external monitor listed (beside the internal one).

Both monitors work fine when I connect one monitor at a time, but together they are always mirrored ...

Any ideas?