If there's any public info about this I'd love to read it.

Both SpaceX and NASA use LabView. NASA has a relatively detailed description of the engine test stands at Stannis:

https://scholar.google.com/scholar?q=NASA+Data+Acquisition+S...

https://scholar.google.com/scholar?q=Design+of+Electrical+Sy...

A typical test stand would have maybe a thousand channels of relatively slow data (pressures, temperatures, flow rates, valve states, etc), and maybe up to a few hundred of channels for essentially audio data from vibration sensors. This amounts to sub-gigabit per second data rate overall.

If very high speed video / multiple video cameras are used, this could generate massive data rates, but unless something interesting happens it is not clear how important this data is.

In flight, the telemetry data rate from the entire Falcon-9 used to be measured in megabits per second per stage, plus the video stream. It was not a huge amount of data. Presumably now with Starlink they send a lot more telemetry from Starship, but in flight the engines typically have far, far fewer sensors compared to the ground testing.