NanoPi M5 26.5.1 UFS install: btrfs root does not boot and manual partition layout is not available

[Gabriel Becker]

Hi,

I would like to report an issue I encountered while testing the new NanoPi M5 UFS boot support in Armbian 26.5.1.

Board: NanoPi M5
Boot media for installation: SD card
Target storage: onboard UFS
BOOT switch after installation: UFS/SD
Tested images:

* `Armbian_26.5.1_Nanopi-m5_trixie_vendor_6.1.115_minimal.img.xz`
* `Armbian_26.5.1_Nanopi-m5_trixie_current_6.18.33_minimal.img.xz`

My current NVMe setup uses a custom layout:

* `ext4` `/boot`
* `btrfs` `/`

I had to use this layout because, in my previous NVMe tests, installing the system directly to NVMe with btrfs using `armbian-install` did not boot when `/boot` was also located on btrfs. With a separate ext4 `/boot` partition and a btrfs root filesystem, the NVMe setup works correctly.

When testing the new UFS installation path, I noticed that the UFS option in `armbian-install` seems to only install the whole system to `/dev/sda1` on the UFS General LUN. Unlike the NVMe installation path, I could not find a way to select an existing target partition or use a manually prepared partition layout.

I tried the following UFS layout manually:

* `/dev/sda1` as `ext4` for `/boot`
* `/dev/sda2` as `btrfs` for `/`

However, after splitting the UFS General LUN this way, the system did not boot at all.

I also tested the default UFS installation path without manually changing the partition layout. I booted from SD card, ran `armbian-install`, selected the UFS install option, and selected btrfs as the filesystem.

With both tested images listed above, the installation process completed, but after removing the SD card and booting from UFS with the BOOT switch set to UFS/SD, the system did not boot.

So the behavior I observed is:

* UFS installation creates and uses only `/dev/sda1` as the system partition.
* UFS installation with btrfs selected completes, but the installed system does not boot afterward.
* A manual layout with separate `ext4 /boot` and `btrfs /` on UFS also does not boot.
* The UFS install path does not seem to provide the same manual partition selection behavior as the NVMe install path.

My questions are:

1. Is btrfs on UFS expected to be bootable at this stage?
2. Or should ext4 currently be considered the only supported/recommended filesystem for UFS boot on NanoPi M5?