If music streamed from TIDAL appears as 16-bit in Volumio even when you expect 24-bit / Hi-Res audio, the issue may be related to the TIDAL streaming quality setting.
In some cases, selecting Highest Rate does not provide the expected 24-bit Hi-Res stream.
Solution:
Open Settings → Sources → TIDAL in Volumio
Locate the Streaming Quality option
Set the quality to Hi-Res instead of Highest Rate
Restart playback and check the track information again
After setting the quality to Hi-Res, compatible tracks should be streamed in 24-bit resolution
Not all albums on TIDAL are available in Hi-Res format, even if different versions of the album exist. If a track is only available in standard or CD quality, it will still be streamed at 16-bit.