I like the Lightburn camera but not having exposure controls caused me all sorts of issues. I got tired of holding cardboard up to block light, etc. so I made a permanent solution.
I have both Exposure and Brightness controls for my Lightburn 8MP camera. When responding to your post, however, I noticed that while I have Auto Brightness as an option, it doesn’t work automatically. For me, Auto Brightness needs to be disabled so I can use the manual adjustment (which works great).
What operating system are you running on your computer? You need to be on Windows 8 or later to get brightness and exposure controls. So if you are (on Windows 8 or later), what have you set for Camera Capture System under settings?