On Ubuntu 18.04 I was able to get the camera working by using some gstreamer libraries from Lubuntu 16.04. I’ve put the stuff up on github but this is how you would try it from a terminal window:
sudo apt install git
git clone http://github.com/dlarue/LightBurnLibs
chmod +x ./lightburn
You should now be able to select a camera and see the image in the Camera tab.
and if you don’t have LightBurn Updater working try installing this:
sudo apt install libssl1.0-dev
Please post your results.