Hey everyone! Below is a community created list of asset locations where you can find and download free assets. Feel free to contribute your own links down below!

• Kenney Assets
• QuaterniusDev
• AmbientCg
• Quixel Megascans (textures and assets)
  
• Free 3D (models)
• PolyHaven (game assets)
• World Machine (terrain generation)
• Glitch game art (CC0)
• Opengameart.org
• https://pixabay.com/

Textures:

• textures.com
• 3DXO
• 3D Textures
• Texturer
• 3D Total

Music:

• https://freemusicarchive.org/search?adv=1&music-filter-public-domain=1&music-fil...

Sound:

• https://freesound.org/browse/

Unreal-only:

• The Epic Games created content: https://www.unrealengine.com/marketplace/en-US/profile/Epic+Games
• The Permanently Free collection: https://www.unrealengine.com/marketplace/en-US/assets?tag=4906

Special thanks to these fine folks for helping assemble this list:
https://itch.io/profile/zesix
https://itch.io/profile/vendaki
https://itch.io/profile/divadriel
https://itch.io/profile/lunacyboard
https://itch.io/profile/letterknumber9