Device tree overlay pi3-disable-bt in Ubuntu Mate?

I would need to work with the hardware serial /dev/ttyACM0 that is currently being used by the Bluetooth system.

Using the soft serial /dev/ttyS0 at 250Mhz is not an option.

this issue can be easily solved in raspbian using a device tree overlay:

However, this overlay does not exist in the /boot partition folder of the provided ubuntu mate image. In fact no device tree overlay is available for ubuntu mate. Is there any reason?

I have tried several things to free the /dev/ttyACM0:

1 - I tried to use the hexx rpi-update system:
(things are deployed to /boot instead of /boot/firmware), nothing changes. Then I mounted /boot on /boot/firmware, kernels update but the startup hangs after after uboot before while loading the kernel

2 - I tried build the kernel by myself following these instructions: , I also get a system that cannot boot

3- I tried to manually copy the boot files from U-boot broke, but if I selected the new kernel in the config.txt file it booted correctly. Some success here, I could make work the pi3-disable-bt overlay and the /dev/ttyACM0 worked, but I lost the wifi functionality. When I tried to copy also the kernel modules the system hanged at boot.

Any idea about how to solve this issue? It looks it should be easy but in practice it is not being easy at all.