A Yoga Slim 7x camera is in PipeWire right after login with the drop-in
On a Snapdragon laptop the camera is missing from PipeWire after every boot, until WirePlumber restarts. A drop-in merged into quattro waits at most five seconds, and on a Yoga Slim 7x the camera is in PipeWire right after login with the drop-in.
libcamera opens each camera's media device once, when WirePlumber starts, and there it fails to open /dev/media0 because permission is denied. On a Yoga Slim 7x, birkskyum measured that gap at 0.2 s, and access that arrives later sends no udev event, so libcamera does not look again.
The drop-in waits until this user can open those media devices, and returns at once on a machine without them. A restart later in the session does not wait. On that Yoga Slim 7x, the Built-in Front Camera is in PipeWire right after login with the drop-in.