Comment 83 for bug 1955383

Did you see the camera lighted up when you open it in webcamtest? Can you attach your kernel log $ journalctl -k -b and $ cat /sys/class/dmi/id/product_sku

The packages are all installed properly. Have you tried oem image from Dell's website? If it doesn't work within Dell's oem image, I think you can request Dell to check the hardware.

https://www.dell.com/community/XPS/Can-t-download-XPS-13-Plus-Recovery-Image-Ubuntu/td-p/8218080