@neilnjae
I briefly looked at trying to remove Adobe DRM from some Google Play books last night & hit a wall because it seems the Adobe e-reader software for windows doesn't currently exist!
I'm currently experimenting with Calibre (spent last night downloading my entire Amazon library and transferring to it) with the intention of seeing how feasible it is to continue using my soon-to-be disconnected Kindle Keyboard independently of Amazon's services.
I still have a Kindle Scribe, but they've already started excluding it from feature updates for the rest of the Scribe range so I'm thinking it'll be my last Kindle and I want to get into more portable ebook habits. I'm not sure how I'm going to manage that on the note-taking front. I know paper + pen exists, but I love the convenience of having all my handwritten notes together, digitally.