I also have an example of how to get all of a single user's comments:
You could use a similar method for submissions. I'm not sure how getting all the stories or comments you've voted on would work, however.
I don't understand the jurisdiction of GDPR very well, but I thought it applied to all EU users.
If you want to do business in some way with the EU, or have your business officers visit the EU, then that is how it works. The EU took a leaf out of the USA "global jurisdiction" book.
To start with you can try this for the public information: http://hnuser.herokuapp.com/user/conroy/json
I wrote hnuser (http://hnuser.herokuapp.com) a long time ago to show karma over time and haven't looked at in awhile but at first glance it seems to still work. It also exists as an npm package if you want to run it from the commandline.