Many of assets in markt place don’t get add to project in unreal 5.1 any plugins to make this possible,
Nope 
But… if it’s something which is just meshes and materials, particles etc, there’s a good chance it will work.
It’s mostly stuff with a lot of code that won’t work. Plugins are definitely out.
But what there is no option, as many good pack like trees, mountain etc that are mesh are not allowed, there must be back end system to upgrade assets, basic free one to next version, or we loose a good set of library
