It worked for me.
I’m using Unity 2020, and since that has a compression bug, I had to turn off GZip compression in the player settings (So go to File > Build Settings > Player Settings > Player > Publish Settings > set Compression Format to Disabled.
I assume when the bug gets fixed the Gzip can be turned back on. Then, following the link from Masked Mouse above, I went there, found the IIS Uncompressed section, and copied and pasted all of that text to a new Text Edit file (I work on a Mac, but not posting to Apache server in my case). Here is the link to the discussion about the bug > Uncaught ReferenceError: unityFramework is not defined at HTMLScriptElement.script.onload (WebGL)
I saved the file, naming it web.config and then copied that up to my server into my build folder. When I reloaded the page, it worked.