GHOST STEMS, EARLY MIXES, TIRAL FILES, ETC...

Recently I've been crossing multiple YouTube channels sharing some raw acapellas, early mixes and vocals + harmonies tracks (probably ripped from Dolby/Tiral Atmos files), and I'm really curious about where are they getting it from. Extracting 5.1 channels, I get it (even though it's complicated), but raw vocals? Demos?

Is there any community focused on Ghost STEMs, etc.?

Edit: I meant TIDAL, I messed up.