John Carter

The deep rabbit hole of (DAS) UBOOT !!
This is not for you if you is running on:
Internal eMMC with factory Android boot loader.
eMMC with updated boot loader but no other boot media.
eMMC with updated boot loader and second boot loader and system on SC-Card and no other boot media (Jump booting eMMC > SD-Card).
eMMC erased / not working and loading boot loader and system and boot loader from SD-Card and no other boot media,
 
But if you is running on:
eMMC with updated boot loader and jump booting to SD-Card with boot loader and booting from there other media.
eMMC erased / not working and loading boot loader (and perhaps system) from SD-Card and jump booting other media.
 
Then jump booting on one SD-Card the UBOOT is loading the init system with first stage of the kernel from the SD-Card.
If have one compatible second stage boot on the SD-Card and UBOOT is loading it it shall being OK.
But as all armbian media have the the same "rootdev=UUID=c6b30a59-8162-46cb-b449-e9615c4a9889" or lable in the armbianEnv.txt on the uboots boot partition its "roll the dice" witch partition the kernel is using then its have loading. If using the SD-Card and its current with the uboot kernel all is OK. But around 50% is using one of the USB media and if its boot partition is not in sync with the kernel its being very strange.
 
If having one SD-Card with latest noble with updated system and kernel 6.16X and putting in one USB-SSD with one old  Jammy and uboot on the SD-Card is booting it is the first kernel loading first stage from the SD-Card (sd /boot) and then mapping the system with /boot from the USB-SSD. The result is very interesting then the old Jammy is coming up with 6.16X kernel but cant loading modules that it need after the first stage  of booting then the /boot/ is the Jemmy with original system and modules that  the 6.16X kernel cant using (but its BOOTING !!!).
 
For booting the system in the right  way its possible caging the "rootdev=" UUID or lable in the armbianEnv.txt on the SD-Cards /boot.
Its working but you is missing the auto select of boot media = if labling the USB-SSD "SSD" and putting in the lable "SSD" it cant boot the system on the SD-Card or other USB devices (and i think its still getting  mixing files from the SD-Card and SSD).
Also formatting the XF4 partition on the SD-Card (not touching the partition table) its booting all USB media OK then uboot is using the system and boot form the USB media and only mini loader from the SD-Card.
Or if having the same system type / version it shall working updating both the system to the same level and have the same hard and software configured on the SD-Card and the USB system media.
 
Normal symptoms is problem with network manager starting all services, Docker service not starting and other services can having problems. Also if installed kernel and the real booted one is not the same its not good then its being miss match of many files its depends on.
 
I have using the erase and sync method and its looks working OK but the sync is more work but can have more systems working OK as backup if somthing is going wrong.
 
As long our UBOOT cant select / and /boot partitions like in X86 systems wi must living with that but if knowing how its working we can living better with it.
 
PS: some version of armbian-config can force witch media to boot from but i have not testing it and its not in the latest version also i have not testing eMMC with updated boot loader and jump booting then the box i testing it on have failed eMMC so only SD-Card boot = no risk for bricking  the system hard and must force mask-rom.
 
So now running  Noble with 6.16.1-edge-rockchip64 kernel !!!