On the page Custom Directory Listings: Scripts, there is an example for "A very simple directory listing script (Python version)" (Example 8-3).
My recommendation is to add an Example 8-4 as "An updated directory listing script in Python."
The following is my own work placed in the public domain:
#! /usr/bin/env python3
# -*- coding: utf-8 -*-
"""Directory Listing Program for Abyss Web Server.

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or
distribute this software, either in source code form or as a compiled
binary, for any purpose, commercial or non-commercial, and by any
means.

In jurisdictions that recognize copyright laws, the author or authors
of this software dedicate any and all copyright interest in the
software to the public domain. We make this dedication for the benefit
of the public at large and to the detriment of our heirs and
successors. We intend this dedication to be an overt act of
relinquishment in perpetuity of all present and future rights to this
software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to <http://unlicense.org/>"""

import cgi
import cgitb
import csv
import datetime
import html
import io
import math

# Public Names
__all__ = (
    'KB',
    'MIME_TYPE',
    'PREFIX',
    'main',
    'write_header',
    'write_body_line',
    'bytes_to_str',
    'utc_to_local',
    'write_footer'
)

# Module Documentation
__version__ = 1, 0, 0
__date__ = datetime.date(2022, 6, 10)
__author__ = 'Stephen Paul Chappell'
__credits__ = 'Aprelium, for providing the inspiration for this program.'

# Symbolic Constants
KB = 1 << 10
MIME_TYPE = 'text/html; charset=utf-8'
PREFIX = '', 'K', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y'

def main():
    """Generate a custom directory listing for Abyss Web Server."""
    cgitb.enable()
    posted_data = cgi.FieldStorage()
    print(f'Content-Type: {MIME_TYPE}\n')
    write_header(posted_data['path'].value)
    with io.StringIO(posted_data['files'].value, '') as files:
        for row in csv.reader(files, csv.excel_tab):
            write_body_line(*row)
    write_footer()

def write_header(path):
    """Create a mostly static header for the directory listing to follow."""
    print(f'''\
<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8">
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <title>Index of {path}</title>
        <style>
            table {{
                border-style: hidden;
                font-family: monospace;
                font-size: smaller;
            }}
            thead {{
                background-color: white;
                position: sticky;
                top: 0;
            }}
            .name, .size, .date {{
                padding-right: 1em;
            }}
            .size {{
                text-align: right;
            }}
            .size, .date {{
                white-space: nowrap;
            }}
            .special {{
                font-style: italic;
                font-weight: bold;
            }}
        </style>
    </head>
    <body>
        <header>
            <h2>Index of {path}</h2>
        </header>
        <hr>
        <main>
            <table>
                <thead>
                    <tr>
                        <th>Name</th>
                        <th>Size</th>
                        <th>Date</th>
                        <th>MIME Type</th>
                    </tr>
                </thead>
                <tbody>''')

def write_body_line(name, url, size, date, mime_type):
    """Create one table row for the current directory/file being processed."""
    print(f'''\
                    <tr>
                        <td class="name">
                            <a href="{url}">{html.escape(name)}</a>
                        </td>
                        <td class="size">{bytes_to_str(size)}</td>
                        <td class="date">{utc_to_local(date)}</td>
                        <td>{mime_type if mime_type else "Directory"}</td>
                    </tr>''')

def bytes_to_str(size):
    """Convert an item's size in bytes to an easily readable representation."""
    size = int(size)
    if size:
        selector = round(math.log(size, KB) - 0.4)
        if selector:
            return f'{size / KB ** selector:.2f} {PREFIX[selector]}B'
        return f'{size:d} {PREFIX[selector]}B'
    return '-'

def utc_to_local(date):
    """Convert the UTC time from the server to be displayed in local time."""
    naive = datetime.datetime.strptime(date, '%Y-%m-%d %H:%M:%S')
    utc = naive.replace(tzinfo=datetime.timezone.utc)
    local = utc.astimezone()
    return local.strftime('%b %d, %Y %H:%M:%S')

def write_footer():
    """Create the document's footer with the current year filled in."""
    print(f'''\
                </tbody>
            </table>
        </main>
        <hr>
        <footer>
            Powered by
            <span class="special">Abyss Web Server</span>
            X1
            <br>
            Copyright ©
            <a href="https://www.aprelium.com">Aprelium</a>
            - 2001-{datetime.date.today().year}
        </footer>
    </body>
</html>''')

if __name__ == '__main__':
    main()