The Sumba languages are a group of clearly related Central Malayo-Polynesian languages.
The most widely spoken Sumba language is Kambera, with a quarter million speakers on the eastern half of Sumba Island.
The Hawu language of Savu Island is suspected of having a non-Austronesian substratum, but perhaps not to a greater extent that other languages of central and eastern Flores, such as Sika, or indeed of Central Malayo-Polynesian in general.
Sumba languages Wikipedia
The Sumba languages are all closely related. Blust (2009) found full support for linking Sumba with Hawu, the most divergent language.Savu languages (See)
Sumbanese: Kambera (dialect cluster), Mamboru