I have created a wordpress plugin that automatically creates the DP feed for you using images you upload through the interface and links to the media in the same wordpress or remotely. It even generates default images if you dont have according to the feed requirements.
Here is a sample feed generated from my plugin https://greektvlite.x-mad.com/?feed=roku_dp
Plugin is free, no plans to monetize it, this is the plugin : https://github.com/upggr/ielko-video-client
This is a work in progress! it also includes a generator for a non DP channel from another opensource project of mine.
I hope I save people some money, I d love your feedback