Full details are here:
Of immediate note (emphasis mine):
Primephonic is no longer available for new subscribers and will be taken offline beginning September 7. Apple Music plans to launch a dedicated classical music app next year combining Primephonic’s classical user interface that fans have grown to love with more added features. In the meantime, current Primephonic subscribers will receive six months of Apple Music for free, providing access to hundreds of thousands of classical albums, all in Lossless and high-resolution audio, as well as hundreds of classical albums in Apple Music’s Spatial Audio, with new albums added regularly.