Flask App deployed (using Docker); TemplateNotFound error

def find_index_html(start_path="/app/app"):
    for root, dirs, files in os.walk(start_path):
        print(root, file=sys.stderr)
        if "index.html" in files:
            return str(os.path.join(root, "index.html"))


@main.route("/")
def index():
    index_path = find_index_html()
    print(find_index_html(), file=sys.stderr)
    # Does index.html exist?
    exist = os.path.exists(index_path)
    if not exist:
        print(f"NOT EXIST", file=sys.stderr)
    else:
        print(f"EXIST\n\n", file=sys.stderr)
    return render_template(index_path)

def find_index_html(start_path="/app/app"):
    for root, dirs, files in os.walk(start_path):
        print(root, file=sys.stderr)
        if "index.html" in files:
            return str(os.path.join(root, "index.html"))


@main.route("/")
def index():
    index_path = find_index_html()
    print(find_index_html(), file=sys.stderr)
    # Does index.html exist?
    exist = os.path.exists(index_path)
    if not exist:
        print(f"NOT EXIST", file=sys.stderr)
    else:
        print(f"EXIST\n\n", file=sys.stderr)
    return render_template(index_path)

def find_index_html(start_path="/dwellist/app"):
    for root, dirs, files in os.walk(start_path):
        if "index.html" in files:
            result = str(os.path.join(root, "index.html"))
            return result


@main.route("/")
def index():
    index_path = find_index_html()
    print(f"Found index.html in: {find_index_html()}", file=sys.stderr)

    # Does index.html exist?
    exist = os.path.exists(index_path)
    if not exist:
        print(f"{index_path} DOES NOT EXIST", file=sys.stderr)
    else:
        print(f"{index_path} DOES EXIST\n\n", file=sys.stderr)
    return render_template(index_path)

def find_index_html(start_path="/dwellist/app"):
    for root, dirs, files in os.walk(start_path):
        if "index.html" in files:
            result = str(os.path.join(root, "index.html"))
            return result


@main.route("/")
def index():
    index_path = find_index_html()
    print(f"Found index.html in: {find_index_html()}", file=sys.stderr)

    # Does index.html exist?
    exist = os.path.exists(index_path)
    if not exist:
        print(f"{index_path} DOES NOT EXIST", file=sys.stderr)
    else:
        print(f"{index_path} DOES EXIST\n\n", file=sys.stderr)
    return render_template(index_path)

# Use an official Python runtime as a parent image
FROM python:3.9-slim

# Set the working directory to /app
WORKDIR /dwellist

# Copy the current directory contents into the container at /dwellist
COPY . /dwellist

# Install latest pip
RUN python -m pip install --upgrade pip

# Install any needed packages specified in requirements.txt
RUN pip install --no-cache-dir -r requirements.txt

# Make port 5000 available to the world outside this container
EXPOSE 5000

# Run app.py when the container launches
CMD ["python", "app.py"]

# Use an official Python runtime as a parent image
FROM python:3.9-slim

# Set the working directory to /app
WORKDIR /dwellist

# Copy the current directory contents into the container at /dwellist
COPY . /dwellist

# Install latest pip
RUN python -m pip install --upgrade pip

# Install any needed packages specified in requirements.txt
RUN pip install --no-cache-dir -r requirements.txt

# Make port 5000 available to the world outside this container
EXPOSE 5000

# Run app.py when the container launches
CMD ["python", "app.py"]

@main.route("/")
def index():
    return render_template("index.html")

@main.route("/")
def index():
    return render_template("index.html")