Stop considering people who aren’t on camera as less engaged. This is just your bias. Your smartest employees understand the additional stress being on camera causes and take every opportunity to limit that effect for themselves. Keep people who are that self-aware.
Recently, I was doing a training session with some new employees and started off by telling them to turn their cameras off. I am fairly sure it was their favorite meeting of their week.
Think about how easy that was. I was showing them how to use a cloud tool, I wanted them focused on the screen, what I was doing and what I was saying about what I was doing. They were. I didn’t need their cameras to tell me that.