If we’re counting Beja presence, then really recently. They were in control of plenty of riverine towns as recently as the 10th century CE iirc.How recent and what kind of Cushitic?
Beyond that, to my knowledge, Lower Nubia could have spoken maybe a West or North Cushitic (perhaps even East, honestly) language up until around the 1000BCE, which though isn’t exactly yesterday, it is comparable in time with the switch in tongues from a Cushitic to Semitic language by our Habesha brothers in Ethiopia and Eritrea.