The first Sony Digital Paper was ten years ago.
https://the-digital-reader.com/sony-...aper-division/
The original reMarkable was 3 years later. The reMarkable 2 is a minor update with more awkward screen, removed the buttons and still essentially a networked PDF device. (WiFi or USB networking) So it's essentially more like the Sony Digital Paper models than like an Onyx, Meebook, Kobo or Kindle model with a digitiser and stylus.
If you want secondhand PDF with sketch freehand annotation, then an original reMarkable may be better value than a reMarkable 2 or a Sony Digital Paper. AFAIK the Sony only connects via the Sony host program. The reMarkable will work on anything with a USB host, USB networking and a browser.
Or a second-hand Fujitsu 10.3″ Quaderno A5 uses about the same screen as all the 10.3″ makes but the Kindle Scribe. It might be less restrictive than Sony software, only the hardware is the same.
https://the-digital-reader.com/fujit...rno-a5-and-a4/