Local USB cameras (Raspberry Pi, Home Assistant)?

[lindsaymarkward]

Thanks so much for frigate. It's great.
I have two USB cameras connected directly to my Pi 4. I had motioneye running (via Docker) for the USB camera streams, working, but quite high CPU usage even though I wasn't using any detection.
I have now added frigate for my RTMP streams but it doesn't have a way to see/stream the USB cameras. I can run motioneye AND frigate, but I think I'm starting to get the Pi doing too much work just for cameras.

Is it possible to get these cameras into frigate?
OR
What is the least-intensive way to stream these USB cameras (for Home Aassistant)? I know systems like Shinobi exist, but would love to hear anyone's actual experience, thanks!