Hi i implemented an online leaderboard using this method: https://www.lexaloffle.com/bbs/?tid=42526. And I managed to get it to work. I can't embed it here because it requires setup on the browser side but if you are interested you can play it here: https://maxall41.itch.io/the-heist. Though the in-game leaderboard can be a little bit glitchy due to the difficulties of parsing json data in PICO-8.