I think researching things that have little internet footprint is an underrated use of LLMs. Most recently, I did quite an extensive research on a card game called "king", variants of which are played in Turkey, Portugal, Brazil, Belgium, France, Russia, Italy, Poland (under the name "Kierki"), and several other countries (but seemingly not known in English speaking countries, despite the English name). It allowed me to uncover scoring patterns that tie various versions together and reconstruct its possible origins and development, however speculative.