We don't have source for the MagicX XU Mini M but we can decompile and recompile its dtbs and unpack and repack its initramfs and rootfs. Our source is a bunch of binary blobs (GROSS). As such this repo only includes scripts to extract and repack our minor changes. I started with the "open" (meaning rom-free) stock TF1 but if you want to make edits you can pickup from the latest Moss release.
Unfortunately macOS doesn't like some of the nodes that get created when extracting a cpio or squashfs (eg. /dev/console) so this all needs to be run in a docker container like my generic-handheld-docker which has handy things like device-tree-compiler and u-boot-tools already installed.