WordPress has a feature called Post Formats, and one of the formats is a “Gallery”.
At the moment, the theme does not output the gallery shortcode on the Blog page but that is something that we are going to add in an update.
So, after the update, you would choose “Gallery” post format for your post, insert a gallery block (or shortcode) anywhere in the post content and the gallery would be used instead of the “Featured Image” when displayed on the Blog page.
You can check our Travel Blog demo to see how different post formats look at the moment (the first post is set to “Video”, the third is set to “Quote”).
Thanks!