when you select text and right click to popup "search google for 'text marked'", here google is your FF's default search engine, but for people in multi-lingual region would prefer to search e.g. in the language of the selected text, which makes more sense for the results.
I wonder if FF could add this function, i.e. auto detect the text's language and search in e.g. google.de, google.cn or google.fr?, which is like the macOS/safari lookup, it detects the text language and point to that dictionary even recognized the grammatical conjugations?