Written in 2022, 4 years ago. Tools and advice may have moved on since.
While researching how to do related content, I came over this excellent article How to Create List of Related Content in Gatsby.JS.
I feel @reckoningdev solution using a custom resolver feels much more like the Gatsby way of solving the use case than many other solutions I found.
His selection criteria are pretty sophisticated, but you could opt for a random selection or any other criteria that makes sense on your site.
We’ll be following this article on tomorrow’s unauthorized and rum-fueled treasure hunt in the sharky waters around the Gatsby islands to add a “related emails” section to my site.
All the best,
Queen Raae