WebGL build stuck at 90% loading? To fix it, go to Edit - Project Settings - Player - Publishing Settings, and change compression format from Brotli, to disabled. (thank BenBonkGames https://forum.unity.com/threads/fix-for-unity-2020-webgl-build-stuck-at-90.94925... for this fix)
You can do that, make another build, and create another itch.io page and upload your game there. I doubt it will count for the game jam, but it would let peolpe try out your game!