The relaunch settled the acceptance-test question by measurement: perf-tray.py hands Ardour RLIMIT_RTTIME=unlimited, so the tray path was never exposed to the 200ms kill that the desktop icon reproduces. On the tray the fix earns its keep on the xrun half instead, and that half verifies: AudioEngine at FIFO/83, nothing at 80, graph back at 50 links.

Two things could not be tested at home and go in writing instead: the UMC202HD, with both failure signatures this box has produced before, and Bluetooth off before the set - because the pre-fix Ardour had no realtime at all, and a WirePlumber restart under a running Ardour is the likeliest way to lose it.