- The next and subsequent times it reads: "[no_device]Bootloader (Teensy 4,.1)".
Seeing "[no_device]" means something is going wrong in Windows. What exactly, and why, I can not say. I can only explain what "[no_device]" means.
Every Teensy reboots, the USB disconnects because it's native USB built into the processor. This is distinctly different from boards like Arduino Uno and ESP32, where the connection is from a dedicated USB-serial chip which doesn't reboot when the main processor does. With Teensy, and with Arduino's native USB boards like Leonardo/Micro/Zero/MKR1000, the USB shuts off while the processor is rebooting. To your PC, it is as if you had physically unplugged the cable and then you quickly plug it back in as the processor boots up again.
When anything about your PC's hardware configuration changes, Windows will send a WM_DEVICECHANGE message to all programs which have requested to be notified of changes. While Arduino is open, the "teensy_ports.exe" program runs in the background to listen for those messages and figure out which Teensy you've connected and what mode it is using.
Typically Windows will send several WM_DEVICECHANGE notifications as Teensy starts up. One is sent when the main USB host controller driver detects the USB device. Then as Windows identifies each interface within the USB device, it will load whatever driver it uses for that interface and send another WM_DEVICECHANGE.
When teensy_ports.exe gets that first WM_DEVICECHANGE, it can see Teensy is present but no drivers have loaded yet. It creates a record so it can tell Arduino to show something when you click the Tools > Ports menu. (how the communication & info is managed between Arduino & teensy_ports is a bit more complicated, but I'm going to gloss over those details) The important thing to know is "[no_device]" is the name teensy_ports assigns when it hears that first WM_DEVICECHANGE and querying Windows for details shows only the main USB device has been detected but the drivers for interfaces haven't loaded. Only a matter of milliseconds later Windows would normally load its built-in HID driver for ID 16C0:0478, which has just one HID interface. When teensy_ports gets that 2nd notification, it's supposed to learn the actual HID interface name and replace "[no_device]" with that info.
Why that's not happening on your Windows machine, I can not say. The best I can do is write this lengthy message to explain how this process is supposed to work. Teensy is appearing to your PC, but for reasons unknown the teensy_ports program either isn't getting that 2nd WM_DEVICECHANGE or Windows isn't giving it the info about the HID interface.