yannick-cw/notionfy
This script reads the clippings.txt from your kindle and syncs all the highlight to a selected notion page. When rerunning it only appends new clippings. Download the notionfy linux zip, unzip it and place notionfy in your PATH or run it directly with ./notionfy. Don't forget to make it executable with chmod +x notionfy.
https://github.com/yannick-cw/notionfy