Complex sentence: Even the black community adopted him as one of their own, as a reported story (that was untrue) was that Ruth had a "secret" black heritage, a story propagated with pride among players in the Negro Leagues.
Split into simpler sentences: Even the black community adopted him as one of their own, as a reported story (that was untrue) was that Ruth had a "secret" black heritage. The myth was propagated with pride among players in the Negro Leagues.