< USB connectable – I recently purchased the PreSonus AudioBox USB96 interface >

The PreSonus AudioBox USB96 interface has the in/out 5 pin MIDI interface connections and the interface's USB connection is to connect the device to the computer. You can use a keyboard that has either the 5 pin outputs or a MIDI USB output. If you purchase a keyboard with the MIDI USB output, you will need an adaptor cable to make the connection between the keyboard and audio interface. A keyboard with the 5 pin in/outs will connect to the audio interface directly.

It appears you're mainly interested in the audio output of the prospective Keyboard you purchase. Note that the Presonus Audiobox USB 96 had two mic/inst inputs and no Line in input. This is not the ideal interface for connecting a Keyboard to the interface. It will work but care must be taken when setting the output of the keyboard and the gain input into the interface and again into the recording software you'll use. Since your purchase is recent, you may want to explore the possibility to exchange the Audiobox USB 96 for the next upgrade in the Presonus line, the PreSonus Studio 24c USB-C Audio Interface. It has all the features of the Audio USB 96 but also has Line In inputs with a reasonable price increase.
BIAB Ultra Pak+ 2021:RB 2021, Latest builds: Dell Optiplex 7040 Desktop; Windows-10-64 bit, Intel Core i7-6700 3.4GHz CPU and 16 GB Ram Memory.