This is not the boot sequence of u-boot bootloader! This is the boot sequence of the board SoC.
Please note that if you flash a partial or bad SPI image, the device might get bricked until the SPI is re-flashed. Since it is the first boot priority, you may have to short one of the SPI data pins with ground in order for the SoC bootloader to skip SPI.
Are there any plans to implement or assist with the tow-boot launcher? It is attempting to provide a BIOS like experience for SBC at the moment.
Link to the Mezzanine tow-boot for example.
https://tow-boot.org/devices/libreComputer-rocRk3399PcMezzanine.html
u-boot 2023.01 will have lots of bootmenu changes. We will reimplement the bootloaders on that version and add the proper menus then.
I see there are tags for 2023.04 in the libretech-u-boot GitHub. Is it nearing completion or working for the RK3399?
AML-S905X-CC is already finished. There is a problem with the upstream kernel IOMMU code holding up ROC-RK3328-CC and ROC-RK3399-PC that our consultancies are working on. Hopefully, the end of this month or the beginning of next month for ROC-RK3399-PC.