Update the API 1 branch

I updated your API branch, but I'd rather have a review.

The main changes: I merged the 3 commits changing the debian dire into a single commit, especialy as one was just a fixup, and the other wasn't relevant enough to be its own commit anymore anymore. I also added a commit to fix the Flatpak manifest.

I am pretty certain I got the symbols file wrong, do you mind checking it out?