motioncomics.io is a web-based tool for creating motion comics. This is an MVP so the features are just enough to create a simple motion comic. Trying it out requires no sign up. Signing up is free.
To show what motioncomics.io can do, here's a motion comic of Attack on Titan chapter 86: https://motioncomics.io/read?v=knSM2BaAc8w