APU2E and bhyve
In order to use Bhyve with passthru you need to go into the config menu and enable iommu and save. That option seems to be available with https://pcengines.github.io/#mr-30 of the firmware.
In addition, give this is AMD you need to enable a tunable according to the end of this page.
Here is an example of what I use for 2 mPCIe cards and igb1/2:
# Turn on passthru support on AMD; # see bottom of https://wiki.freebsd.org/bhyve/pci_passthru hw.vmm.amdvi.enable=1 vmm_load="YES" pptdevs="3/0/0 1/0/0 4/0/0 5/0/0"