It seems like there only are a few select test partners that Spotify supports up to 24 bits initially. According to Electrocompaniet the rest of has to wait. "While Spotify offers up to 24-bit quality, they've confirmed that the 24-bit SDK is currently limited to a few select test partners. This means most hardware manufacturers, including Electrocompaniet, are waiting for the broader 24-bitsupport rollout from Spotify."
Spiral Groove/Soundsmith - jRiver/Audiophile Optimizer/Process Lasso - Devialet 1000 pro - Rockport Ankaa
Nordost Valhalla2, Brahma, Frey2+ & Tyr2/Ansuz Mainz C/D8
Nordost Valhalla2, Brahma, Frey2+ & Tyr2/Ansuz Mainz C/D8
Isoacoustics OREA/Shunyata Dark Field/Nordost QV/QK
Devialet Gemini
