Hello,
After difficulties to set it up, I finally found the solution for me (and probably for others in the same situation), as I could see my stream on OBS but no image on Lightburn. Then, I found a clear and easier solution to install everything on my Pi (I’m a total begginer with raspberry).
First, I followed this video: Install motion
And then from the “Setting up you windows pc” of this page: Raspberry Pi as a webcam
So, I installed IP Webcam App
And it works 
Hope it will help.