When I used Godot 4.0 a few months ago for a game jam I did have some issues on Itch io with the WebGL but I think it has since been fixed. To get it working I you just need to make sure you use the "Compatibility" Renderer (it is an option when you make a new project). Also when you export, make sure you use the name "index.html" for the web build (Godot will use the project name by default when exporting). And when you submit to Itch io make sure you check the box that says "SharedArrayBuffer support — (Experimental) This may break parts of the page or your project. Only enable if you know you need it"
I am using Godot 4.1 and tested it earlier today and it worked correctly for me with very little problems. It is always good to test that your builds are working on Itch io early in the jam (I do it as soon as I get something on screen), to avoid the stress closer to the deadline.
Thank you r0ckems0ckem! That helps a lot. Mostly worried about the compatibility with various browsers but sounds like the Compatibility render would get me what I need. And definitely would experiment but really wanted to learn the newer version instead of having to the older Engine. Guessing most things would be transferable, but I don't know what I don't know yet. LOL
All the beset on your Jam!