AFAIK, there’s no way to directly change the furigana. You may be able to indirectly change it by editing the sentence to combine kanjis so that the “parser” can interpret it as “one word” instead of two separate requests for two separate words. which may also change the furigana.
With that said, you can’t modify the LingQ curated lessons (at least to my knowledge.) In this case, you could download the audio, copy the text from the lesson, and then reimport it. With that work, you may still have incorrect kana.