According to the
Libby FAQ, only the OverDrive apps for iOS, Android, and Windows 8/10 are being sunset at the end of April. "The legacy OverDrive for Windows and OverDrive for Mac desktop software that allows users to download audiobooks and transfer them to dedicated MP3 players will
not be sunset at the end of April. While we no longer support new downloads of this software, users who already have it installed can continue to use it by downloading audiobooks from your library’s .overdrive.com website." [emphasis added]