For anyone else wanting this (to always use summary_large_image) - I’ve taken @Terrapop s code and made it into a plugin you can include:
https://github.com/CubeCoders/discourse-twitter-large-card.git
- https://github.com/CubeCoders/discourse-twitter-large-card
What I’d really like to do is something similar to the Github card you’ll see attached to this post, a way to automatically generate dynamic cards for a given topic. Right now the card will be the first decent-sized image in the post. So if you create a post that starts with an image, it’ll end up using that.