I had the exactly same issue and solved a few days ago. All the devices in IOMMU group 10 should be listed in syslinux configuration such as
Here is mine:
Once rebooting, the check box from System Devices will be enabled and you can select
Though Fix Common Problems plugin reports it as a warning, I think it is OK to ignore for now.
I think there must be an elegant way to do it without warning, but I cannot come up with a solution now.