In your first screenshot, you have all the paths set to publish to the uncategorized category. If you want to publish all posts to the same category you only need to create one Embeddable host record.
The Path Whitelist values that you have added to your Host entries might be causing problems. You can leave that value blank to publish all posts from your blog site that you’ve added the Discourse embed script to. If you want to set a specific path to publish to a Discourse category, the path should end with /.*
. For example /sites/.*
The double slash at the start of your /t/newsletter-discussions/105
path may be a problem. Also, that looks like the path to a Discourse topic. If set, the path should be the path to a grouping of posts on your blog. The purpose of the Path Whitelist setting is to allow you to publish posts from a specific path on your blog to a specific Discourse category.