In the marketplace submission guidelines there is no information about requirement of LODs. So this is up to the content creator if they choose to offer LODs. Honestly, it’s in their benefit to offer LODs because it makes their assets more efficient with minimal additional work.
There are options for creating LODs. Typically these involve a 3d modeling application though. If you have a access to 3Ds it’s pretty simple and without much headache (IMO). You can see my process for doing this here: https://forums.unrealengine/showthread.php?56777-Photons-Be-Free-Mini-tutorials-and-other-curiosities&p=227697&viewfull=1#post227697
Simplygon offers a plugin for UE4 that can do this (not sure what their plugin cost is). https://www.simplygon/