Re: DRM removal and calibre
I have a Kindle, the other half a Kobo. I buy DRM'd books from both. They are both loaded into Calibre which allows unlocking and transfer to the other device. It is a bit of a faff, but I find it worthwhile.
Kindle books must be downloaded to a PC. Then Calibre has no trouble with them.
Kobo books are de-drmed with a Kobo plugin called Obok de-drm.
I find calibre is a major benefit for ebooks and I donate regularly as it is a free install and updates are made every couple of weeks.
Microsoft have form on this issue I once foolishly downloaded some films that needed MS DRM servers and they just shut them down with no warning and this was about 10 years ago.