Add-on replacements: - Linguist for translations. - Search by Image for reverse image search (there are others that just use Google Lens directly, but I use this one).

Cast is a bit more cumbersome. There is fx_cast on GitHub, but it requires a companion app. Firefox seems to want to add cast based on a flag you used to be able to enable, but I'm guessing there are some restrictions from Google's end they ran into.