Apple recommends using Motion 5 to create animated iMessage Stickers. That's what I did. However, as you know, animated stickers must be in .apng or .gif. Gif does not support transparency. And Motion 5 does not export in .apng, only .mov and .m4v. I can find no .mov or .m4v to .apng converters.
So how are other Developers making animated stickers with transparent backgrounds? For clarification, what I mean by animnated are Motion 5 Behaviors (in this case Grow/Shrink - four png layers and two of them have Grow/Shrink Behavior applied).
(And why does Apple recommend using one of their apps that doesn't export the required format?)