Can I run a normal PC mobo with this power supply? My fear is that the cable from the 4+4 pin is too short. Thanks for the help!
In general, it is possible to connect a normal mainboard to this power supply, if all the required connections can be reached, but it is not intended for such a usage scenario, because besides the connections themselves, an additional external power supply (up to 160W) is needed, which has to be purchased additionally

I have done it with a very similar cable

Intertech Mini-ITX PSU Rev.2
THERE THE FIRST PHOTO DOESN'T STICK, it has the same connectors as this 160 watt mini PSU....

and a Mini-ITX board (with Ryzen3200G).

Combined with an external power supply, it's a very quiet solution for an HTPC.