When I go to your website Flarum doesn't boot, but I don't see any Flarum related error in the browser console either. That's strange.
Does your forum loads if you disable your extension ? I see you're including google tags and firebase libraries, are you sure those aren't the ones blocking Flarum load ?
I see multiple "unreachable code after return statement" warnings in the console, but it seems to come from google tag manager.
Looking at your code I can't see what's wrong. this.setting() is only available in the admin, so your change from the previous messages is correct. You can also replace app.forum.data.attributes[attributeName] with app.forum.attribute(attributeName) but either will work.
No need to copy the dist file for us here, as long as you make sure you re-build it each time you edit the source file π