Hi,
uuu -lsusb shows no “Known USB Device,” indicating that the i.MX8M Plus has not successfully entered ROM Serial Downloader or USB SDP mode, or that the USB OTG device has not been properly enumerated by the PC.
Combined with the inability to connect via JTAG and the TDO signal remaining high, this appears to be an early-stage board-level bring-up issue: the SoC may not have released the reset properly, there may be abnormalities in critical power supplies or clocks, the boot mode strap may not have been sampled correctly, or there may be issues with the connections or power supply to the JTAG/USB-related pins.
Best Regards,
Zhiming