Phased array radar systems provide efficient utilization of their link budgets by focusing antenna radiation in a particular direction. Same frequency Simultaneous Transmit and Receive (STAR), also known as In-Band Full-Duplex (IBFD), capabilities more efficiently use array resources enabling execution of multiple tasks in parallel rather than relying on time-division multiplexing (TDM). Fully digital arrays ease dynamic aperture reconfiguration enabling different subarray regions to be used for STAR by application. Additionally, focusing exclusively on digital techniques for self-interference cancellation (SIC) avoids the need for specialized radiators or analog circuitry, keeping front-end hardware relatively simple. Arrays with more integrated processing resources can reduce or eliminate the need for centralized processing, improving scalability. Of course, the particular algorithms employed, data communication, and distributed processing strategies together with hardware determine scalability. This paper discusses ongoing work in support of scalable-STAR arrays with a focus on the interconnected digital backend and a testbed used for these development efforts.