Adding React app to Flask under URL prefix

I have a React app that I want to reside on a specific url route prefix of a Flask app.

Examples:

• host.com/ is the home page of the Flask app. It's index.html file in the templates directory (using standard Flask conventions here).

• host.com/about is another page of the Flask app. It's some other file in the same templates directory.

• host.com/search is the root of the React app. I want anything with /search prefix to reference some part of the React app.

• host.com/search/123 is some page of the React app (following the above logic). I am using react-router-dom for routing inside React app.

I built the React app with npm run build and then tried serving just the React app with Flask like in this example. Everything worked fine.

Then I attempted the following to put React at specific url prefix of the Flask app:

# file app.py

import os
from flask import Flask, render_template
from .search_blueprint import search_blueprint

app = Flask(__name__)
app.register_blueprint(search_blueprint, url_prefix='/search')

@app.route('/')
def index():
    return render_template('index.html')

if __name__ == '__main__':
    app.run(use_reloader=True, port=5000, threaded=True)

And here are the contents of the search_blueprint.py file (very similar to the answer to the question that I already mentioned:

# file search_blueprint.py

from flask import Blueprint, send_from_directory
import os

build_dir = os.path.abspath('./app/static/build')
search_blueprint = Blueprint('search', __name__, static_folder=build_dir)

# Serve React App
@search_blueprint.route('/', defaults={'path': ''})
@search_blueprint.route('/<path:path>')
def serve(path):
    if(path == ""):
        return send_from_directory(build_dir, 'index.html')
    else:
        if(os.path.exists(os.path.join(build_dir, path))):
            return send_from_directory(build_dir, path)
        else:
            return send_from_directory(build_dir, 'index.html')

The Flask index.html page that is referenced in app.py loads fine when I go to host.com/. When I go to host.com/search I get a blank screen (meaning no errors from Flask). In the console there's an error message like this:

Loading failed for the <script> with source “http://host.com/static/js/main.ca656ef1.js”.

Anyone knows why I can't get this React app work at a specified url prefix?

Here's the directory layout relevant to the question:

app
├───static
│    └───build
├───templates
│    └───index.html
├───app.py
└───search_blueprint.py

Edit

Adding contents of build directory:

build
│   asset-manifest.json
│   favicon.ico
│   index.html
│   manifest.json
│   service-worker.js
│
└───static
    ├───css
    │       main.d293ea0a.css
    │       main.d293ea0a.css.map
    │
    ├───js
    │       main.ca656ef1.js
    │       main.ca656ef1.js.map
    │
    └───media
            logo.5d5d9eef.svg