To my understanding, they mapped all of the CC bindings from their digital mixer into Reaper and then routed the audio through JACK. They had a double monitor setup that seemed to be running a pretty standard Reaper setup (with Bitwig as an optional backup), as well as a smaller integrated monitor in the dashboard of the mixing console (which must have been running a custom UI). They were hooked up to a pretty sizable NAS, and they made a pretty large emphasis on separating project files from the OS. It seemed like the secret to their workflow was weekly backups of the OS partition with redundancy for the mission-critical components. Their round-trip latency was also pretty impressive, with less than 10ms for software sources and 30ms for hardware sources. All of it was running on an older Threadripper workstation.