Snap packages are in containers which prevent them from "seeing" outside of those containers unless you give them permission.

For VLC, I'd recommend uninstalling the Snap package, and using the vanilla APT version:

sudo snap remove vlc
sudo apt update && sudo apt install vlc

You will be able to run VLC as root by modifying the VLC binary, located in /usr/bin

First, you'll need a hex-editor, like Bless :

sudo apt-get install bless

Then, you'll open the VLC binary with the hex-editor :

sudo bless /usr/bin/vlc

Search and change the geteuid string by getppid, save and exit.

You can now launch VLC as root.