I am the person who reported the issue you have linked. I am still with Ghost and developing themes. In case you like to see those, please visit https://gbjsolution.com/
I was not able to solve the issue that’s why I am using a workaround. At the time of development, I insert the card CSS and javascript from a live production site via code injection.
<link rel="stylesheet" type="text/css" href="https://mylivesite.com/public/cards.min.css?v=db70eba112">
<script defer="" src="https://mylivesite.com/public/cards.min.js?v=db70eba112"></script>
If you inspect your live site, within <head> tag you will find CSS and JS. Copy those two lines and add those in your local development site’s code injection.
You are good to go with local development.