v4l2loopbackをコンパイルする手順を実行すると、次のようになります。 https://www.arducam.com/docs/cameras-for-raspberry-pi/pivariety/how-to-access-and-program-the-pivariety-camera-using-command-line-python-opencv-and- gstreamer/#22-create-a-virtual-video-node-access-by-python
正しい lib/modules/version にあるモジュールが見つかりましたが、読み込めませんでした。
[13952.844293] v4l2loopback: disagrees about version of symbol cpu_hwcap_keys
[13952.844320] v4l2loopback: Unknown symbol cpu_hwcap_keys (err -22)
[13952.844401] v4l2loopback: disagrees about version of symbol device_create_file
[13952.844410] v4l2loopback: Unknown symbol device_create_file (err -22)
[13952.844431] v4l2loopback: disagrees about version of symbol _dev_err
[13952.844440] v4l2loopback: Unknown symbol _dev_err (err -22)
[13952.844771] v4l2loopback: disagrees about version of symbol device_remove_file
[13952.844781] v4l2loopback: Unknown symbol device_remove_file (err -22)