You can use your Canon EOS R * on Ubuntu as a webcam, we can’t use the canon webcam utils on Ubuntu, but we have another way to do it. I have tested it on the R, RP and R5, I suppose on the R6 it works too and is quite simple;)
First install gphoto and v4 utils:
sudo apt-get install gphoto2 v4l2loopback-utils
Plug in your camera via USB (when the camera mounts automatically, unmount it).
Then run this command to see if your camera is capable of doing this.
gphoto2 --abilities
Result for EOS RP
Then run this to activate the kernel module needed to create a video device from your camera.
sudo modprobe v4l2loopback
Check the video devices you are using with the command
v4l2-ctl --list-devices
Choose a video number not in use, in my case the 6 is not in use. Then run:
gphoto2 --stdout --capture-movie | ffmpeg -i - -vcodec rawvideo -pix_fmt yuv420p -threads 0 -f v4l2 /dev/video6
This will create a video device in /dev/video6, which you can now use in programs like OBS or VLC.
If you see any errors about the device being in use you need to kill the gvfs-gphoto2-volume-monitor process by running:
killall gvfs-gphoto2-volume-monitor
Thanks to https://askubuntu.com/a/915204 although I made some changes 😉