Running this through Itch I'm getting the error during the Unity loading screen:
Unable to parse Build/GLOVESUltraWebGL.framework.js.gz! This can happen if build compression was enabled but web server hosting the content was misconfigured to not serve the file with HTTP Response Header "Content-Encoding: gzip" present. Check browser Console and Devtools Network tab to debug."
I love FIST and was really excited to find your game/tool. Let me know if there's anything you know that may help!
Found this in the FAQs is there an install option button in the itch.io app?
Itch.io App + WebGL [resolved] - itch app Development - itch.io