Repeat slideshow in iOS 11 (or 12) on the iPhone

I am trying to have a repeating slideshow on my phone for a birthday party. Apple showed me a YouTube video for iOS 9. They said I could do it from a share sheet but I didn’t really find that. Any help here?

I think Photos will export a slideshow to a movie, then you could loop the movie. Another option is to put the photos in a keynote presentation, export to a movie, and loop the movie.

Thanks, but I don’t see how to loop the movie.

It’s been available for a couple of years. I’ve never tried it on any iOS device but I found these instructions which might help: