MCUBoot aborts with sysbuild/mcuboot layout for nRF54L15DK

Question

Hello, In the latest nRF Connect SDK 3.2. , I've been having a few "sysbuild/mcuboot/boards" folder layout issues with nRF54L15DK / nRF5340DK when using external device FLASH & MCUBoot. 
 Other existing projects using nRF9150DK and nRF52840 (with 4MB SPI FLASH) boards are successful in builds and application executions. 
 However, with nRF Connect SDK 3.2.1, the “sysbuild/mcuboot/boards” works for nRF52840 device with external FLASH but not for nRF54L15DK and nRF5340DK. 
 I think the issue is probably a configuration one but have been unsuccessful trying a few variations. 
 The issue can be reproduced with the DevAcademy "Lesson 9 Bootloaders and DFU/FOTA", Exercise 3 – DFU with external flash for nRF54L15DK. 
 The DevAcademy, l9-exercise 3 "sysbuild" folder layout works fine for nRF54L15DK / nRF5340DK. However, as I typically target the same application for different boards, I prefer to keep the .conf &.overlay files for the boards in their respective “boards” folder for both the application and MCUBoot. 
 The layout shown below works fine for nRF9151, nRF52840, and Thingy53 projects with NCS 3.2.1. The layout doesn't work for nRF5340DK and nRF54L15DK. 
 I can build the projects successfully but MCUBoot fails with an "abort()" when starting the bootloader. *** Booting My Application v2.3.0-dev-0d9411f5dda3 ***
*** Using nRF Connect SDK v3.2.1-d8887f6f32df ***
*** Using Zephyr OS v4.2.99-ec78104f1569 ***
I: Starting bootloader
D: context_boot_go
abort() 
 I expected the following console output: *** Booting MCUboot v2.3.0-dev-0d9411f5dda3 ***
*** Using nRF Connect SDK v3.2.1-d8887f6f32df ***
*** Using Zephyr OS v4.2.99-ec78104f1569 ***
I: Starting bootloader
I: Primary image: magic=unset, swap_type=0x1, copy_done=0x3, image_ok=0x3
I: Secondary image: magic=unset, swap_type=0x1, copy_done=0x3, image_ok=0x3
I: Boot source: none
I: Image index: 0, Swap type: none
I: Bootloader chainload address offset: 0x17000
I: Image version: v0.0.0
I: Jumping to the first image slot
*** Booting nRF Connect SDK v3.2.1-d8887f6f32df ***
*** Using Zephyr OS v4.2.99-ec78104f1569 *** 
 
 The following "sysbuild/mcuboot" layout for nRF52840 device with external FLASH (spi_xenon_v2) builds and runs successfully. 
 The issue can be reproduced with " DevAcademy, l9-exercise 3", with the following "sysbuild/mcuboot" layouts. I don't see anything obvious that may be incorrect with the MCUBoot configuration. 
 The folder structure used for the nRF54L15 (and similar for nRF5340DK) and conf/overlay files are listed below. The application fails with "abort()" . 
 I would appreciate if you could please review and check if this layout builds and runs successfully for you on a nRF54L15DK? Thank you. 
 "spi" project for nRF54L15 using external FLASH. 
 spi_nrf54l15_v2/boards/nrf54l15dk_nrf54l15_cpuapp_ns.overlay.overlay: 
 /* Add external flash to application */
&mx25r64 {
 status = "okay";
};

/ {
 chosen {
 nordic,pm-ext-flash = &mx25r64;
 };
};
 
 spi_nrf54l15_v2/prj.conf: CONFIG_GPIO=y

# Enable mcumgr DFU in application
CONFIG_MCUMGR=y

# Enable MCUMGR management for both OS and Images
CONFIG_MCUMGR_GRP_OS=y
CONFIG_MCUMGR_GRP_IMG=y

# Configure MCUMGR transport to UART
CONFIG_MCUMGR_TRANSPORT_UART=y

# Dependencies
# Configure dependencies for CONFIG_MCUMGR 
CONFIG_NET_BUF=y
CONFIG_ZCBOR=y
CONFIG_CRC=y

# Configure dependencies for CONFIG_MCUMGR_GRP_IMG 
CONFIG_FLASH=y
CONFIG_IMG_MANAGER=y

# Configure dependencies for CONFIG_IMG_MANAGER 
CONFIG_STREAM_FLASH=y
CONFIG_FLASH_MAP=y

# Configure dependencies for CONFIG_MCUMGR_TRANSPORT_UART 
CONFIG_BASE64=y

# Enable SPI driver for the application
CONFIG_GPIO=y
CONFIG_SPI=y
CONFIG_SPI_NOR=y
CONFIG_SPI_NOR_SFDP_DEVICETREE=y
CONFIG_SPI_NOR_FLASH_LAYOUT_PAGE_SIZE=4096

# QSPI drivers are enabled by default for some chips.
# Disable it explicitly to be sure QSPI is disabled.
CONFIG_NORDIC_QSPI_NOR=n 
 sysbuild/mcuboot/boards/nrf54l15dk_nrf54l15.conf: 
 # Enable logging for MCUboot
CONFIG_LOG=y

# Turn on a LED so we can see when Serial Recovery mode is active
CONFIG_MCUBOOT_INDICATION_LED=y

# Enable SPI driver for external flash (MCUboot)
CONFIG_GPIO=y
CONFIG_SPI=y
CONFIG_FLASH=y
CONFIG_SPI_NOR=y
CONFIG_SPI_NOR_SFDP_DEVICETREE=y
CONFIG_SPI_NOR_FLASH_LAYOUT_PAGE_SIZE=4096
CONFIG_NORDIC_QSPI_NOR=n

# required by SPI driver
CONFIG_MULTITHREADING=y

# Increase number of sectors
CONFIG_BOOT_MAX_IMG_SECTORS=512

# nRF54L15 needs some more space for MCUboot.
# so remember to optimize this size in your own project
CONFIG_PM_PARTITION_SIZE_MCUBOOT =0x12000 
 sysbuild/mcuboot/boards/nrf54l15dk_nrf54l15.overlay: 
 / {
 aliases {
 mcuboot-button0 = &button1;
 mcuboot-led0 = &led1;
 };
};

/* Add external flash to MCUboot */
&mx25r64 {
 status = "okay";
};

/ {
 chosen {
 nordic,pm-ext-flash = &mx25r64;
 };
}; 
 sysbuild/mcuboot/prj.conf: 
 MCUBoot takes the CONFIG_PM_PARTITION_SIZE_MCUBOOT from " sysbuild/mcuboot/prj.conf" file. However, for nRF52840 / nRF9151, I find that MCUBoot can take the MCUBOOT size value from the board ".conf" file, rather than the "sysbuild/prj.conf". Question - Is the " sysbuild/mcuboot/boards/nrf54l15dk_nrf54l15.conf" effectively merged with the " sysbuild/mcuboot/prj.conf"? If so, shouldn't the board ".conf" take priority? 
 # Disable Zephyr console
CONFIG_CONSOLE=y

CONFIG_FLASH=y

CONFIG_LOG=y
CONFIG_LOG_MODE_MINIMAL=y 
CONFIG_LOG_DEFAULT_LEVEL=0
CONFIG_MCUBOOT_LOG_LEVEL_DBG=y

### Use picolibc to reduce flash usage
CONFIG_PICOLIBC=y

# nRF54L15 needs some more space for MCUboot. 0xF000 is chosen somewhat arbitrarily,
# so remember to optimize this size in your own project
CONFIG_PM_PARTITION_SIZE_MCUBOOT=0x16000 
 sysbuild.conf: 
 # MCUboot
SB_CONFIG_BOOTLOADER_MCUBOOT=y
SB_CONFIG_PM_EXTERNAL_FLASH_MCUBOOT_SECONDARY=y
SB_CONFIG_PM_OVERRIDE_EXTERNAL_DRIVER_CHECK=y

SB_CONFIG_BOOT_SIGNATURE_KEY_FILE="\${APP_DIR}/custom_keys/ed_ci_key.pem"
SB_CONFIG_MCUBOOT_SIGNATURE_USING_KMU=y
SB_CONFIG_BOOT_SIGNATURE_TYPE_ED25519=y
SB_CONFIG_MCUBOOT_GENERATE_DEFAULT_KMU_KEYFILE=y

Kind Regards