RPI4 Raspbian 64 bit & LinuxCNC

try

sudo apt-get install libgl-dev

and then

sudo apt --fix-broken install

Sorry that did not work
I still get this error

npacking libgl-dev:arm64 (1.3.0-7~bpo10+1) ...
dpkg: error processing archive /var/cache/apt/archives/libgl-dev_1.3.0-7~bpo10+1_arm64.deb (--unpack):
trying to overwrite '/usr/include/KHR/khrplatform.h', which is also in package libraspberrypi-dev 2+git20200520~143707+2fe4ca3-1
Errors were encountered while processing:
/var/cache/apt/archives/libgl-dev_1.3.0-7~bpo10+1_arm64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
pi@raspberrypi:~ $

Sorry I am sure I must be doing or have done something wrong. I have downloaded the .deb file but cant install them ether.

This seems to be a known issue:

github.com/raspberrypi/Raspberry-Pi-OS-64bit/issues/14

so maybe try:

sudo apt update
sudo apt full-upgrade

and then the above suggested

sudo apt install libgl-dev
sudo apt --fix-broken install

I have tried everyone of these in every way I can think of and I always get the same error.

dpkg: error processing archive /var/cache/apt/archives/libgl-dev_1.3.0-7~bpo10+1_arm64.deb (--unpack):
trying to overwrite '/usr/include/KHR/khrplatform.h', which is also in package libraspberrypi-dev 2+git20200520~143707+2fe4ca3-1
Errors were encountered while processing:
/var/cache/apt/archives/libgl-dev_1.3.0-7~bpo10+1_arm64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
pi@raspberrypi:~ $

are you sure you did the

sudo apt update

before
sudo apt full-upgrade

Do you really need deb packages?

Why not just build and run LinuxCNC in-place?