This issue is covered in the Setup Guide which also includes a Troubleshooting section if the not detected problem occurs. For my case the issue that caused the "No cameras available" when running 'libcamera-hello --list cameras' command was having Legacy camera support enabled on the Raspi SBC. This causes the system to detect cam as "raspi camera" with device as /dev/video0 regardless of version. With this device id I could not get the 'webRTC' service to work and had to use 'Adaptive MJPEG-streamer', defeating my reason for using crowsnest, real time streaming video. Having Legacy Support enabled is the correct way to get the cam working if not using crowsnest, which was my starting point when I added crowsnest to my already running printer setup. Once I disabled Legacy support the system detects the Pi cam as 'libcamera' with device id as listed in the guide. There is currently no mention of this circumstance in your guide or troubleshooting information. Would suggest you add this info in the setup guide as well as to the troubleshooting information.
You can easily duplicate this issue by running 'sudo raspi-config', enable Legacy support it will blank screen the webrtc stream every time on my setup.
Thanks for all your work I'm really impressed with the improved camera performance with this working.