The briefing tells us to look at the homepage.

Solution

The way to solve this challenge is by looking at the source code. After right-clicking on the homepage and selecting "View Page Source" we can see a comment in the HTML:

...

		If you visit a page and it returns a 404 error, then that page really doesn't exist, don't bother trying to uncover anything.
        </strong> 
	<!-- Here's your reward for reading the above rules: flag{challenge1-vptjkAdLZCbrGKwsfbgGErZxd} -->
</div>

...

Our flag is:

<aside> 💡 flag{challenge1-vptjkAdLZCbrGKwsfbgGErZxd}

</aside>