Official site: Unreal Engine
Distributed material: 3D Models, 3D Scenes, 3D Materials, Assets
Format: UASSET

Description:
This set contains a huge number of additional assets for Unreal Engine v.4.xx – 5.xx (some of them do not indicate the UE version, so you’ll have to make sure by scientific poker whether it’s suitable or not..).
The build includes assets such as: materials, sound effects, blueprints, visual effects, weapons, environments and much more.
The full list of assets and which versions of UE they are suitable for is below under the spoiler.

Please note: you will not find anything by the name of the topic on the official website of the market, because… This collection of assets is unofficial and hand-built.
Some assets by their own name can still be searched in the store and sold, but some can no longer be, please take this into account.