Yocto how to build mender with external device tree

Yes but in the case of

MENDER_UBOOT_AUTO_CONFIGURE = “0”

you it does not really matter what KERNEL_DEVICETREE is set to as it will not be used later. Meaning you can set it to

  KERNEL_DEVICETREE = "whatever"

This will silence u-boot-mender-common.inc error, but could potentially trigger an error elsewhere.

But the proper solution is to provide a patch that implements

" To provide a MENDER_DTB_NAME which takes precedence of KERNEL_DEVICETREE if already defined."

Something like,

    if [ -n "${MENDER_MENDER_DTB_NAME_FORCE}" ]; then
        MENDER_DTB_NAME="${MENDER_MENDER_DTB_NAME_FORCE}"
    else
        MENDER_DTB_NAME=$(mender_get_clean_kernel_devicetree)
    fi