I've created a basic extension for this, where a loop is created over all <img> tags, and data-fancybox is added as an attribute. It is also 100% compatible with fof/upload
It's clean, and works in my instance. See a demo over at https://metabullet.com
I will be extending this so that Youtube and other videos can take advantage of the same thing.
EDIT: Uploaded 🙂
It's basic, but functional. Further development to follow
To install
composer require phenomlab/fancybox
To update
composer update phenomlab/fancybox
To remove
composer remove phenomlab/fancybox
