KVM - Add PCI error

I installed the KVM plugin on a new machine; if I create a VM and select a device from the 'Add PCI' menu (in this case, an ethernet adapter), I get the following error upon startup:

Unable to - poweroninternal error: qemu unexpectedly closed the monitor: 2025-07-16T13:11:16.403915Z qemu-system-x86_64: -device {"driver":"vfio-pci","host":"0000:03:00.0","id":"hostdev0","bus":"pci.1","addr":"0x0"}: vfio 0000:03:00.0: failed to setup container for group 15: Failed to set iommu for container: Operation not permitted

OMV\Exception: Unable to - poweroninternal error: qemu unexpectedly closed the monitor: 2025-07-16T13:11:16.403915Z qemu-system-x86_64: -device {"driver":"vfio-pci","host":"0000:03:00.0","id":"hostdev0","bus":"pci.1","addr":"0x0"}: vfio 0000:03:00.0: failed to setup container for group 15: Failed to set iommu for container: Operation not permitted in /usr/share/openmediavault/engined/rpc/kvm.inc:2679
Stack trace:
#0 [internal function]: OMVRpcServiceKvm->doCommand()
#1 /usr/share/php/openmediavault/rpc/serviceabstract.inc(124): call_user_func_array()
#2 /usr/share/php/openmediavault/rpc/rpc.inc(86): OMV\Rpc\ServiceAbstract->callMethod()
#3 /usr/sbin/omv-engined(544): OMV\Rpc\Rpc::call()
#4 {main}

I already have 2 other OMV installations running various VMs, but this is the first time this happens to me.

You made me doubt, so I checked (even though, to be honest, on this old server VM-Ware used to run before). I attached a screenshot, but I would say that everything is active as it should be.

I took a look at the groups with the command: find /sys/kernel/iommu_groups/ -type l

The result is what can be seen in the attached screenshots.

The motherboard of this server has 5 integrated ethernet ports (it is a server board).

But if they belong to the same group, theoretically I could assign them all at once to a VM or simply, they cannot be assigned at all? As for the bridging, no, I don't want to do that, because at that point OMV would also become reachable from those ports and that annoys me.

I did a quick test by assigning both ports of the group to a VM, but it still doesn't work. I will look into it further when I have time.

Thanks.