Thanks again — I wanted to add one more observation.
On the Mac mini direct USB path, the DA2 appears to disconnect cleanly when it enters standby. I tested standby 5 times, and all 5 times I immediately saw “USB Device Missing” in the logs. When the DA2 is turned on again, it reconnects immediately and playback works normally. In practice, I had used the Mac mini direct USB path for a long time without this standby/on problem.
That seems different from the LHY Audio RPI Pro USB host path. In the earlier testing with reset-on-disconnect logic, there did not seem to be a detectable disconnect event there. So from my side, the DA2 standby transition looks clearly visible on the Mac direct USB path, but not in the same way on the LHY Audio RPI Pro path.
I’m not sure yet whether this points to a path-specific interoperability difference or something specific to the LHY Audio RPI Pro USB host path, but it seems like an important difference.