Works.. okay.

Starts disabled which makes it seem like its not working at first, only functions on "Write this in English" questions (doesn't work on wordblocks for instance), and there's a noticeable delay for loading the furigana on each question.

Otherwise it does what it intends to do and there's no better options, so hey.

ありがとう

I was waiting for official support of the Furigana from Duolingo, but guess it'll take some time. I really like this extension. Pretty convenient. Thank you, Cieric