I had no issues with atf for R4Pro yet,only uboot and linux have to use lower frequency (48MHz vs. 50MHz) to work.
Is there an option to connect a card to use wifi 6?
Would be nice if one of the SFPs was Gpon, so people can use that to bypass their ISP ONT.
That’s the job of an SFP/SFP+ GPON/XGSPON transceiver, not the router itself.
As long as you find one within the power budget for the SFP+ port (3W on the regular BPI-R4, I believe) with a properly configured EEPROM it should presumably work if the SFP+ slot is fully functional at this point in time.