Here's a simple but proven media player application for rtts/debian, intended to run on a keyboardless computer attached to the back of monitor used as a turn-on-and-forget media player.

Open the file ~/.xsession and add the following line:

path/to/play.sh &

Turn on the computer and insert a USB flash drive containing one or more media files. play.sh will pick them up automatically and start playing them.

Attach a keyboard and open a terminal. From there, you're on your own.