Favicon

Check: https://realfavicongenerator.net/favicon_checker

https://stackoverflow.com/a/48969053/4034572 → Use https://realfavicongenerator.net

https://evilmartians.com/chronicles/how-to-favicon-in-2021-six-files-that-fit-most-needs

Says rel="shortcut icon" is not necessary, just use rel="icon". Also mentions this article: https://mathiasbynens.be/notes/rel-shortcut-icon