There are recordings of the Jubilee Singers late in their career I think. As to being dated nowadays: well, they were performing 150 years ago, it's not very surprising! They got hammered by some their own people, as did other great black performers(eg Leadbelly and Louis Armstrong), for being Uncle Toms, and doing what the white man wanted to hear. Well the music has lasted better than the critics, I am glad to say. Steal Away, Swing Low Sweet Chariot and Go Down Moses etc will be sung for a good while yet, I have no doubt.
Thanks to Adrian Mitchell for his last play, bringing a great topic to life, and thanks to his widow Celia Hewitt for adapting it and getting it on the radio.
A final footnote(not mentioned by Adrian, I don't know if he was aware of the fact). The writer of Swing Low and Steal Away was probably not black at all, but a Red Indian/Native American.