Linux behaviour today with the dock and enclosure #7

Part of #1

Question

What happens on Linux today when the dock and the NVMe enclosure are plugged into each port of the J516M?

Checklist:

1. Before plugging anything in, enable dynamic debug for thunderbolt, thunderbolt_apple, phy_apple_atc, pcie_apple and tps6598x.
2. For each port, plug in the enclosure, then the dock with a monitor. Capture the kernel log, lsusb -t, /sys/bus/thunderbolt, /sys/class/typec, and drm connector status.
3. Note whether anything enumerates: USB 2 or USB 3 fallback, the dock's USB hub, its display output, or nothing at all.

The answer records the per-port behaviour, with trimmed log excerpts.

Watch for (from Why no NHI binds on the J516M): the NHI is only created on USB4 mode entry, so this plug-in is the first attempt ever made on this machine. Enable dynamic debug for drivers/thunderbolt/apple.c and drivers/usb/typec/tipd/core.c too. Record whether apple_cio_start() runs, whether RTKit boot fails (the expected failure, since the T6031 ACIO uses the M1 start sequence without MxWrap), and, if the NHI does bind, whether its ring interrupts fire (the transmit and receive interrupt order may be swapped).