I was able to make the card show up in DSM!!!! You gave the hint with the extra VM options.
For this card, and maybe other GTX1650 cards, the trick in UNRAID is to hide the hypervisor too.
How? After the VM is created, it has to be edited in XML View and this lines have to be included to the end of the domain section, just before </domain>:
<qemu:commandline>
<qemu:arg value='-cpu'/>
<qemu:arg value='host,kvm=off,hv_vendor_id=null,-hypervisor'/>
</qemu:commandline>
Without it, the card was recognized by DSM (lspci -q shows the NVIDIA graphic card) but not used. Now it can also be used inside DSM.