Can confirm Metahuman plugin is available for 5.1 in the Marketplace now!
Btw it was possible previously to import Metahumans using Quixel bridge in 5.1, however it wasn’t possible to do Mesh-to-Metahuman and other features that required the Metahuman plugin, until the plugin was released for 5.1. Which it is now! Thank you, Unreal and Metahuman team!