I don't have have an answer to your question, but one major factor that one should consider when making a popularity comparison between Flutter and React Native

I don't have have an answer to your question, but one major factor that one should consider when making a popularity comparison between Flutter and React Native is that _React_ part. Most problems and questions that developers encounter while working on React Native applications are not specific to React Native, but rather React itself. As such, I find it likely that many RN developers don't always use "native" in their search terms.