VLC media player has got to be one of the most popular ways of watching media files in the world. And video is not the only media it plays. In fact it plays just about everything, on just about everything, without charging you anything.
Being an open source product itself, VLC media player is of course installable on KDE neon. Simply open up Konsole and install it by typing,
sudo apt install vlc
then enter your admin password and wait for the installation to finish.
After it has installed VLC can be opened either by going to the Application Menu and either selecting it and typing VLC or by visiting Applications/Multimedia.
Tips for VLC on KDE neon
VLC will probably already be installed on KDE neon and as far as I know works in exactly the same manor as it does on other operating systems. Probably the easiest way to get it to open a file is to right click the file and choose VLC in the resulting menu. This only works if it is registered in File Associations to play the file.
If you wish to get it to open something else or to make it the default for a file type you can either change or add it in Application Menu/Applications/Settings/ then open System Settings and browse to Applications/File Associations (Remember you can shortcut this by searching File Associations on the Application Menu).
A far easier way is just to right on the file then select Open With and then Other Application, in the resulting windows tick the Remember Application Association box at the base, choose VLC under the Multimedia menu drop down and select OK. Sounds harder than it is.