Such a minor quibble that I’m almost embarrassed to mention it, but it would be nice to have these if possible.

I’ve migrated the search.json.mozl4 (I think?) file I had in my FF profile folder, which has quite a lot of custom search engines I’ve accumulated over the years, so that may have something to do with it, but I think the favicons might have been missing out of the box? Anyway, like I said, a minor quibble.