Godot 4.0 broke web exports without a webpage having certain headers(over my head content), but sites like itch have those things. I believe the explanation was because of having mulit-threaded support in the engine.
I have held off upgrading from 3.5 because my games I publish on my simple github page and that change on 4.0 would not work on my github page.
There was rumor of providing a single threaded web mode in future releases(4.1 was mentioned), but don’t know if this happened. I check release notes every few months but haven’t seen if this change has been made.
Are web exports fixed for godot now?
I have managed to deploy my game to Gitlab Pages through the use of the godot-coi-serviceworker addon from the Godot addons library. Should probably work as well for GitHub.
https://github.com/nisovin/godot-coi-serviceworker/
The way this works is by creating a secure context through a service worker running in the background, which allows Godot to use SharedArrayBuffer to communicate between Threads etc.
Which means you don’t have to have the headers if you can’t configure them for your hoster (although if you can that’s still preferable as there is probably some JS overhead at least when loading the page with this).