Yet, there are some marketplace assets already upgraded to 5.0 EA
On the " No Content Found" there is a link → Join the conversation and tap into the creative power of our active Marketplace community. Inspire others with your ideas or find new uses for already existing content!
That page says " Oops! That page doesn’t exist or is private."
I’m sure this will eventually be fixed, just wanted to point it out.
Noob hint: Besides plugins, you can always choose an older engine version and force import it and it should work.