According to my understanding, the acronym sud refers to latter-day saints - the name of members of The Church of Jesus Christ of Latter-day Saints. Tribune is the name of one of his magazines. But it catches my eye that they combine Spanish (sud) with English (tribune). It should be Lds-Tribune (Latter-Day Saints).
SUDTRIBUNE from German, is actually S.D.R., means stands on the south side (of the Dortmund stadium). By antonomasia this is called the southern stands of the Borusia-Dortmund stadium, the loudest in all of Europe.