Custom board with Static partitions, MCUboot and Sysbuild

Hello!

I am using an nRF Connect SDK V2.9.0 with a nrf54l15. I want to set up a project with a custom board. I want to add DFU in the future, so there must be MCUboot bootloader and static partitions defined.

I took the zephyr/samples/sysbuild/with_mcuboot sample. Then I compiled it for the nrf54l15dk. From the build directory, I took the partitions.yml file and copied it as pm_static.yml to the root folder of my project. I enabled the partition manager in the sysbuild.conf file, compiled the project again and flashed it - everything works fine and the board prints some logs, as described in the sample readme.

Then, using the VScode extension, I have created a custom board. And I slightly adjusted it:

1) Enabled UART, so I would be able to get some logs, when I run the code on a nrf54l15dk

2) Added missing zephyr,flash-controller chosen node

3) Reduced the boot_partition size to 48K, so it matches the pm_static.yml

The code compiles for the custom board, but when I flash it and reset the board - nothing happens.
Using a debugger, I found out that the bootloader starts, but is unable to find an image. Also, for some reason, logs are disabled in the bootloader.
With a help of the nrfjprog, I have dumped the MCU's memory and inspected the dump. In the dump, I can see the image at the expected address.

So the problem is that I cannot properly set up the project for a custom board, while it works fine for a board from the SDK.
Here is a repository with my code, that exposes the issue I am facing: link