There are multiple ways to access Kindle highlights.
For e-books I loaded myself onto my e-ink Kindle (e.g. using Calibre), and for the hightlights made on a specific e-ink Kindle: connect that Kindle to laptop, and copy the file myclippings.txt
For highlights from all the e-books I bought (actually leased) through Amazon, regardless of Kindle devices or apps: https://read.amazon.com/kp/notebook
While reading a book on an e-ink Kindle, open the three dot menu, select Notes, and export notes, and it will be send to the e-mail address connected to my Amazon account.
There are multiple ways to access Nova2 highlights/notes:
Attach device over USB and download files to disk or to e.g. Zotero
Sync note files to Evernote and export/process from there.