OBS doesn't see V4L loopback devices as inputs

[ali1234]

How to reproduce:

1. Install v4l2loopback-dkms
2. sudo modprobe v4l2loopback max_buffers=2 exclusive_caps=1 video_nr=10 card_label="VirtualCam"
3. Start a program such as backscrub which feeds the loopback: backscrub -c /dev/video0 -v /dev/video10 -m /usr/share/backscrub/models/selfiesegmentation_mlkit-256x256-2021_01_19-v1215.f16.tflite -d -d
4. See the preview window from backscrub indicating that everything is working
5. Open obs-studio
6. Add a V4L2 capture source
7. "VirtualCam" is not listed in the available sources
8. Run mpv av://v4l2:/dev/video10 and see the virtual camera output. Close it.
9. Run any other program that captures video such as Skype, Firefox etc and see that VirtualCamera is available.

[ali1234]

Source configuration not showing the VirtualCam input:

What it looks like for someone who does all the above but using OBS 26.1.2 from Debian 11:

See floe/backscrub#105 for more details.