By default, the bootloader is not included in any SWU package. To include the bootloader artifacts in the update package so they are programmed during installation, set the SWUPDATE_UBOOTIMG variable in your project’s conf/local.conf configuration file to true:

conf/local.conf
SWUPDATE_UBOOTIMG = "true"

By default Digi Embedded Yocto will pack the bootloader of the default variant of the ConnectCore 6UL in the SWU image. To update a SOM with different SoC revision or RAM memory, specify the correct bootloader file on your project’s conf/local.conf as follows:

conf/local.conf
SWUPDATE_UBOOT_NAME = "<bootloader-filename>"

See U-Boot files by variant.

Updating the bootloader is a critical operation. Make sure the bootloader has been verified to boot properly before using an SWU package to update it, especially if doing a remote update.