I just wanted to interject that I ran into the same (non?)-issue on the 25.8.1 trixie minimal image using a rpi400. armbianmonitor -u

I have only ever seen mmcblk?boot? Partitions on media that was setup for Android as the A/B is part of how Android installs updates and can fall back to the previous version. I've never seen them on an Armbian created media.

Wow, I didn't know those command and mechanism even exist... Thank you for your tip! Any ideas regarding main (mmcblk2boot) topic question, perhaps?

It's worth noting that you don't have to necessarily change anything in the build process. As long as you plan to not insert partitions in the middle, you can: write the image to the card with parted, resize the root partition to whatever you want make a new partition If you want to have more than 4 partitions total, this works best with GPT partition table, but legacy msdos works too with a little more effort `fsck.ext4 -f /dev/foo` where foo is the root partition `resize2fs /dev/foo` after you have the machine booted, you can then mkfs the new partition [you could probably do it in advance of booting the system too] I do this regularly, b/c I typically only partition about 1/2 or 1/4 of the SD card to leave the rest for wear-leveling. Are you trying to do this as a one-off or are you trying to do it for a dozen or more SBCs of the same type?

not everything is mounted, at least not in the way you expect it. check "swapon -s"