I did read those documents, though they don't document how to build modules, where/how to copy them to the SD card for the specific linux kernel version (uname -a) . I was confused why the board does not use the root /boot folder Image.
1. checking uboot: it does use "Image" as the boot name.
2. The dts is defined by uboot.
it seems the FRDM-IMX93 board boots Image from mmcblk1p1 and not the rootfs /boot folder on mmcblk1p2 that has the Image with the LTS Image as wel.. After replacing Image on p1, it worked. Not sure why the Image is on /boot then ?
However now I face that modprobe cannot find the modules copied to the SD, even they are in the correct lib/modules folder, even they came from the same build tree..
P.s: Having the dts hardcoded by uboot is a bit inflexible. rather prefer uboot show a menu which dtb to boot