You’ve already found my " Papers to DEVONthink" script:
If this script doesn’t work anymore, I could look into updating it (and, as time allows, I may even be able to fine-tune it to your needs). Which macOS & DT versions are you using? And do you actually have any PDF annotations stored in Papers 3, or is it mostly PDFs & publication metadata?
If you also have Bookends (which can integrate with DT e.g. via a special template or via scripting), you may also want to look at my “Papers to Bookends” script. This script exports all publications selected in your Papers 3 library to Bookends (see the script’s Readme on how to facilitate the import of PDF annotations).