Suku is another Bantu language of the DRC of uncertain classification. Traditionally, it's classified as a Yaka language, but it's also been claimed that it's a Kongo language or a Pende/Holu language (i.e. more closely related to Pende, Kwese, and perhaps Mbala). I suppose it may be spoken in the ROC as well, since apparently, this clip is of singing in Suku but from the ROC:
https://www.youtube.com/watch?v=sgn8GCrJbpI