The Keynote for AR by Apple seems very promising and very advanced already! It’s called Reality Composer.
One beloved feature in Keynote, “Magic move”, is not included yet but prototyping AR Experiences is no longer a thing that needs to take weeks, tons of money and specialized skills, but something that any UX/UI designer can experiment with.
And it’s not only a Prototyping tool. You can then export your AR experience for others to play with or to include in other apps or embed in web sites.