I am using nRF Connect SDK v2.2.0 with nRF52810 on a custom board.
We have included OTA updates in our project, and it works successfully and downloads the firmware via MQTT and writes it using developer.nordicsemi.com/.../dfu_target.html.
Because the internal flash nRF52810 is not enough for us, we want to use the external flash AT45DB0 to store the firmware image.
As an example I used tests\modules\mcuboot\external_flash.
As a result of the build, I get an error:

I made a child_image\boards .overlay file:
Fullscreen123456789101112131415161718192021/ { led { compatible = "gpio-leds"; but_led_1: but_led { gpios = <&gpio0 12 (GPIO_PULL_UP | GPIO_ACTIVE_LOW)>; label = "Permission to turn off the device"; }; }; aliases { mcuboot-led0 = &but_led_1; }; chosen { nordic,pm-ext-flash = &at45db0; };};&gpio0 { status = "okay";};
I made a child mcuboot.config file:Fullscreen123456789101112131415161718192021## Copyright (c) 2021 Nordic Semiconductor ASA## SPDX-License-Identifier: LicenseRef-BSD-5-Clause-Nordic#CONFIG_MAIN_STACK_SIZE=10240#CONFIG_PM_PARTITION_SIZE_MCUBOOT=0x10000#CONFIG_MBEDTLS_CFG_FILE="mcuboot-mbedtls-cfg.h"CONFIG_MCUBOOT_INDICATION_LED=yCONFIG_FLASH=yCONFIG_FPROTECT=yCONFIG_PM=nCONFIG_FW_INFO=y#CONFIG_BOOT_ENCRYPT_EC256=n#CONFIG_BOOT_ENCRYPT_RSA=n#CONFIG_BOOT_ENCRYPT_X25519=n#CONFIG_BOOT_SWAP_SAVE_ENCTLV=n
Added pm_static.yml file static partition to the root of the project:
Fullscreen123456789101112131415161718192021app: address: 0xc200 end_address: 0xfa000 region: flash_primary size: 0xede00external_flash: address: 0xee000 end_address: 0x800000 region: external_flash size: 0x712000littlefs_storage: address: 0xfa000 end_address: 0x100000 placement: before: - end region: flash_primary size: 0x6000mcuboot: address: 0x0 end_address: 0xc000
I spent a lot of time to understand why it doesn't work. I hope you can help me.
I can provide you with the source files of my project if you need them.