"Core is an endless arcade of thousands of free games to play and worlds to explore designed by a global community of developers. Play thousands of Unreal-powered games in every genre imaginable, or create, share, and earn from your own!"

...

"As a Creator on Core, you have access to the full power of the Unreal Engine, thousands of free, professional music, art, and sound assets, and an industry-leading monetization system."

https://www.coregames.com/create

https://docs.coregames.com/api/

Cheers!