Screen blanking is a very common problem on the default Pi install. I wrote up some fixes here a while ago: https://shutdownscanner.com/blog/posts/raspberry-pi-digital-...

These days you're probably better off using something like Screenly: https://www.screenly.io/ose

I have a fork that I hacked some basic auth into here: https://github.com/jpsingleton/screenly-ose