I really dislike that browsers, specifically firefox requests a favicon even when I don't specify one. This bothers me because I usually have the console open and I see the request failing and it's just annoying. The browser shouldn't be making requests automatically, sites already do enough of that.
Anyway, I found a really good solution for it which is to embed a null png as a base64 encoded image in the html.
<link rel="icon" href="data:;base64,=">
With that no more extra requests. I've since added this to all of my pet projects and made it part of the base template that I use.
Some related reading:
The story of how the favicon came to be:https://thehistoryoftheweb.com/how-we-got-the-favicon/
A bug report about gifs being sent as favicons from 2001:https://bugzilla.mozilla.org/show_bug.cgi?id=111373
Github issue about someone's gemini client making favicon requests:https://github.com/makeworld-the-better-one/amfora/issues/199