Why am I seeing a 404 (Not Found) error failed to load favicon.ico when not using this?

By adding this to the header section, you will definitely remove the error in the console log:

<link rel="shortcut icon" href="">

From Chrome 2020 this is the solution :

<link rel="shortcut icon" href="#">

Because your browser always looks for the favicon.ico even if you don't specify it within your HTML.

So I'd suggest just creating one and placing it in the root of your website.

Google favicon generator and make an icon. Name it favicon.ico and drop it in your webroot.

See if this helps.

Also here is a tutorial on favicon: https://www.w3.org/2005/10/howto-favicon