Oh sure.
UEFI can be written to both eMMC and SPI FLASH I think.
The current PCIe driver in UEFI does not work correctly at all.
For example, I draw four NVMe from me, although I actually have one. All this is very strange.
If you add PCIe2 support then UEFI can add support for 2.5GbE Ethernet via the driver provided by REALTEK UEFI UNDI Driver for RTL8125
This may look very good on Rock 5B.