https://unsplash.com/images/stock

https://www.textures.com/

https://www.gameart2d.com/freebies.html

https://www.pexels.com/videos/

https://opengameart.org/

https://pixabay.com/

https://picsart.com/create/editor?category=photos

https://deepai.org/machine-learning-model/image-editor

https://www.fotor.com/features/ai-image-generator/

https://www.youtube.com/c/kmmusic/about

Kevin MacLeod 

An artist who releases all their music with a Creative Commons by Attribution 3.0 license 

https://sonniss.com/gameaudiogdc

Sonniss - GameAudioGDC

Every year Sonniss gives away thousands of sound files during the Game Developers Conference

https://www.kenney.nl/assets

Mixamo 

An Adobe library of animations that can be imported into Unity 

https://www.mixamo.com/#/

Kenney

Free 2d and 3d game assets which are mostly universal creative commons