Hey @MrMasterbit. I recently used a high score server for a game deployed on Itch. It isn't public yet (it's pre-release) but plenty of people have used it and successfully posted scores to my server. I had to set the score server up myself, and then used the Fetch API to post scores there.
IIRC the key part was setting `mode: 'cors'` in the `fetch` config, and using the correct headers on the server: `Access-Control-Allow-Origin` was set to `*` and `Access-Control-Allow-Headers` set to `Origin, X-Requested-With, Content-Type, Accept`.