@RamonR: I have covered how to get annotations from Kobo devices in
https://www.mobileread.com/forums/sho...01#post3215101. There is one method I can think of that is missing, but, it doesn't work with firmware later than 3.19.x.
As to feeding to other systems, it has been mentioned in the past, but not discussed much. From what I can tell, I don't think many people are using annotations on these devices in way that this would actually be useful. Personally, my use is limited to marking errors to fix and something to look up later. I don't know if any of the methods above are suitable for feeding to these other systems. It is probably possible to change some to be more suitable, but, it would depend on what is needed and how much interest there is.
And as you are interested in using Readwise, you should hassle them. I read their FAQ and what they say for the Kobo devises is a cop-out. Especially as they include instructions for using the "My Clippings.txt" file from a Kindle. It isn't as convenient if you have to plug the device in, but, it is possible and would expand their market.