Install RT Kernel and LinuxCNC 2.9 on Rpi4

After helping a chap on the IRC to get Debian 11 with a RT kernel running on his Rpi4 I took notes and created a step by step.

gnipsel.com/linuxcnc/rpi4-11.html

I built a deb and put it on github so it's 3 commands to install LinuxCNC.

gnipsel.com/linuxcnc/rpi4-11-emc.html

JT