@WildEnte Folders always have a folder icon 😉
I'm not actually sure how relevant the Favicons file is, as search engines are defined in the Web Data file and it has a url for the favicon there:
$ sqlite3 "Web Data" "select short_name,favicon_url from keywords;" Bing|https://www.bing.com/sa/simg/bing_p_rr_teal_min.ico Yahoo!|https://no.search.yahoo.com/favicon.ico DuckDuckGo|https://duckduckgo.com/favicon.ico Ecosia|https://cdn-static.ecosia.org/static/icons/favicon.ico Startpage|https://www.startpage.com/sp/cdn/favicons/favicon--default.ico Wikipedia|https://no.wikipedia.org/static/favicon/wikipedia.ico Google|https://www.google.com/favicon.icoIf it doesn't work, look in the Settings > Search list what the icon is.
Try resetting search engines to default.
Worst case, you could delete the Web Data file, this will nuke and reset all your search engines obviously but might fix the problem, and if you have no custom engines it's no problem doing that.