Over in the Sony forum on July 11, BobVA reported that Kobo told him they are updating their system to indicate in the store if a book is compatible with Sony readers. However, that was nearly two months ago.... in the meantime they suggested the workaround already mentioned above - checking for Blackberry in the "read this on" area
https://www.mobileread.com/forums/sho...=241151&page=2