There seems to be something wrong with the privileges of the deb package.

[matoken]

When the deb package is introduced, the file permissions are those of the user who introduced the package.

$ sudo dpkg -i ./obs-v4l2sink.deb
$ ls -la /usr/lib/obs-plugins/v4l2sink.so /usr/share/obs/obs-plugins/v4l2sink/locale/
-rwxr-xr-x 1 mk mk 90832 Jul 25  2018 /usr/lib/obs-plugins/v4l2sink.so

/usr/share/obs/obs-plugins/v4l2sink/locale/:
total 16
drwxr-xr-x 2 mk mk 4096 May  8 18:58 .
drwxr-xr-x 3 mk mk 4096 May  8 18:58 ..
-rw-r--r-- 1 mk mk   87 Jul 25  2018 en-US.ini
-rw-r--r-- 1 mk mk   92 Jul 25  2018 zh-TW.ini

I checked it on Ubuntu 20.04 LTS amd64 & Debian sid amd64.