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.
I’m having the same problem. There are bugs about it open with the developers, so presumably it’ll be fixed at some point.
Search Icons are missing again #2227
Icons are missing from custom search engines added from settings #2261
In the meantime, I was able to make my search bar presentable by installing the “Search Engines Helper” plugin and manually adding the search engines that are having favicon problems, then going into the search engine settings and removing the checkmarks for the broken ones.