Hello, thank you for creating this board and making it open source, as well as providing a great documentation.
Just have a couple of notes regarding building with the latest NRF SDK:
Zephyr has moved to sysbuild, you have to create a file called sysbuild.conf and add SB_CONFIG_BOOTLOADER_MCUBOOT=y to it in-order to build for MCUBOOT bootloader. Adding CONFIG_BOOTLOADER_MCUBOOT=y in a regular conf file will get overridden at build time.
You can also add -DSB_CONF_FILE=<sysbuild-conf-file> in CMake build settings
app_update.bin has been renamed to zephyr.signed.bin
If your mcuboot partition is larger than flash partitioned for it (as was case with me) modify mcuboot conf file and set CONFIG_LOG=n to save some space, the conf is located at /home/ncs/v2.9.0/bootloader/mcuboot/boot/zephyr/prj.conf
Make sure newtmgr is set to baud=1000000, exactly not less not greater
