same issue.
openwrt kernel version 5.4.101
BCM57810S 10G SPF+ card (PCI-E slot)
proxmox has been passthough successfully and signed to openwrt(VM), but in openwrt it failed to load, even not loaded by kernel.
the driver version: bnx2x-firmware_20201118-3_x86_64.ipk and kmod-bnx2x_5.4.105-1_x86_64.ipk