tested u-boot 2019.07 on CZ11NIC20 that features Bank gpio@71_ (boot.scr probes gpio input gpio@71_4) and with the symlink /boot/dtb removed SPF is automatically detected.
5 LED rescue (Unsecure SSH) through did not work.
N.B. querying u-boot version via ssh cli with strings /dev/mtd0 | grep 'U-Boot 20'