Download https://raw.githubusercontent.com/videolan/vlc/master/share/lua/playlist/youtube.lua file. and copy that file to /usr/lib/x86_64-linux-gnu/vlc/lua/playlist and rename youtube.luac as youtube.luac.orig and rename youtube.lua as youtube.luac.

More luas in https://github.com/videolan/vlc/tree/master/share/lua/playlist