I keep a list of NASAxx flight IDs in my flightaware but have not seen any flights for several months. By N numbers search it has been the same story. Wentt back several hundred flights from Ellington Field and no flights by NASA nor n with NA suffix.
It only affects the FAA datafeed so if the data is available via another path (e.g. the aircraft is transmitting an ident and it’s been correctly set) then it’s still available that way.
e.g. if you look at NASA524’s tracklog you’ll see that all the data is via ADS-B; there is no FAA radar or arrival/departure data.