I am new to Unreal and I have 8 years of experience on Unity.
I have found no documentation whatsoever for mobile development. And I have been stuck for 2 weeks replicating a simple AR app that I already did on Unity in 4 hours.
I am not joking… There is absolutely no documentation for professional AR development.
I will tell you even more…
If you want to use the latest ARCore version, you will have to build Unreal from source code!
Don’t believe me? check for yourself the official ARCore quickstart for Unreal ("QUICK"start lol)…
For mobile development, Unity is year-lights ahead of Unreal in terms of documentation. For other platforms, I have no idea.