Password Protected site without username Amplify AWS

Question

I am trying to set up a simple password protected website. I have a main page that is a landing page with an input box for the site password on it. The users will enter the password and then be routed to a different main page with content and a the rest of the sites links. Currently I am attempting to do this on AWS Amplify with a static site but with no lick. I have also tired to use Google Firebase again with no luck.

Ideally it is something that will do a check to an environment variable that contains the password on the server side. I am attempting to run this server less so the following implementation methods would not work. It is similar to how they do it Here, but on a static hosting service like AWS Amplify or Google Firebase.

This is how I would look to do it with Flask. I am still trying to learn reactjs so if there is some way to securely do a check similar with it before loading each page that would be ideal.

@app.route('/', methods=["GET" , "POST"])
def homePage():
  if current_user.is_authenticated:
    return render_template("homepage.html")
  if request.method == "GET":
    return render_template("login.html")

Then simply add the check for is user authenticated before loading each page and if not dump back to the landing login page. All of the other solutions that I have seen 1, do not allow for custom landing pages where the password is entered (this is a MUST have) and 2 also require that there is a username in addition to the password, again this is a must that there is not and it will only require the user knowing the generic password.