User blog comment:MisterWoodhouse/The first Unified Community Platform release is now live for NEW wikis/@comment-31593032-20200313002811/@comment-37336800-20200313005409

I went and tested, all three gallery types work. You can see the results here if you're curious.

I'm not sure if it's still planned but at one point in time the removal of slideshows was being thought about as part of New image galleries.