The best UX for 404 error page [Practices + Examples]
A 404 Page - Best Practices and Design Inspiration - WPKlik
404 Error Images – Browse 3,209 Stock Photos, Vectors, and Video
How can I find 404 pages?
404 Error Page UI Design: Turning Frustration into Delight
Handling 404: Page not found error in Flutter
Documention
Error 404 – what is it and how do I fix it?
Why should a 404-error page return the correct HTTP status code
Error 404: What It Is and How to Fix It in Five Simple Steps