can't get this to work in DW 2021 on a Mac Big Sur

Keep getting errors

TypeError: window.DMX.setStrictMode is not a function. (In 'window.DMX.setStrictMode(true)', 'window.DMX.setStrictMode' is undefined)
(anonymous function) — jquery.min.js:2:31711
jquery.min.js:2:31711

TypeError: e.indexOf is not a function. (In 'e.indexOf(" "', 'e.indexOf' is undefined)

TypeError: undefined is not a function (near '...DMX.loadFiles...')

any ideas how to fix this

Where and when are you getting these errors?
I just tested the lightbox in DW CC21 and it works fine.

I was using it here but had to stop on this page imaginationtables.com/_it/admin_pages/product_listing_form.php?it_table_id=1

I think this may be related to Bootstrap 5

I replicated the errors page again

here was where the Lightbox errors are

imaginationtables.com/_it/admin_pages/product_listings_2.php

But that has nothing to do with DW CC2021, it's an error with the scripts on the page.
The jquery version bundled with the lightbox extension is 1.11, while on your page i see you are using 3.6.
Try changing the jquery include to /ScriptLibrary/jquery-latest.pack.js instead, to see if the error disappears.

This is already included

<script type="text/javascript" src="/ScriptLibrary/require.js"></script>
<script type="text/javascript" src="/ScriptLibrary/jquery-latest.pack.js"></script>
<link rel="stylesheet" type="text/css" href="/Styles/dmxEditor.css" />
<script type="text/javascript" src="/ScriptLibrary/dmxEditor.min.js"></script>

Not sure what you mean or what needs to be changed

That is not included on the link you provided: imaginationtables.com/_it/admin_pages/product_listings_2.php
There i don't see the dmxzone jquery include but the include coming with template you are using:

<script type="text/javascript" src="../_Admin_Templates/HTML/vendor/jquery/jquery.min.js"></script>