Sadly there seems to be no generally accepted definition of the term “Compilation” amongst the different metadata providers (and users).
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“Greatest Hits” albums: A collection of previously released tracks of an artist
Mostly all marked as compilation in Roon -
Soundtrack: Can be a collection of tracks from different artists used in a specific movie
In my library not marked as compilation -
Tribute albums: Can be a collection of tracks best known from a specific artist, interpreted here by other artist(s)
The compilation mark seems to depend on the album (artist) credit
See also this older thread: