Originally Posted by HarryT
An alternative would have been to install "Kindle for PC", download it there, copy to Calibre, and convert to ePub.
If it's available, yes. But as I mentioned above, I've seen some ebooks that are not available for the kindle apps. And if you have no compatible device... then the only available option is the Cloud Reader (or an alternate bookstore). It seemed to me that that was the situation the OP was in.