One of the obvious omissions in previous WavPack versions was not accepting Apple's ubiquitous AIFF audio format as a source, and this has been remedied in WavPack 5.6.0. Also there is improved handling of PCM files that claim to be a non-whole-byte depth (e.g., 12-bit) but aren't actually (i.e., they have non-zero "padding" bits).
The cmake support has been greatly improved, including building WavPack as a subproject and utilizing external toolchains like MinGW-w64, which can actually now build the Cool Edit / Audition and Winamp plugins. Also, support has been added for the Open Watcom compiler and targeting OS/2.
For the remaining minor fixes and improvements, see the official NEWS file.
Note that I am no longer able to generate binaries for macOS. These should probably be obtained from HomeBrew anyway, and that's now been updated to 5.6.0.