No USB serial with Teensy 4.x compiled Optimize: Debug

I would suggest you look at VisualMicro with Visual Studio.
It sits on top of the Arduiuno IDE and therefore, via the Arduino IDE has PJRC support.
It also has excellent debugging capabilities.

Can I suggest in future that when you make a post, that you review it using the "Go Advanced" button.
This may have highlighted to you that you were about to make a post with an erroneous link.

I deleted the http:// from the start of the text box for the link. It must get put back in again when you hit OK.

Mea culpa!

I give up.
Things happen! The number of typos I have caught by using the "Go Advanced" is extremely large.
I also check every link (at least most of the time) before I click post.

I just wish most people would check their post before posting it.
There are some very well regarded posters that sometimes (read quite often) make posts with sentences that are just Gobbledegook (<--I just had to put my original spelling into Word and do a spelling check to get it correct).
One thing I have discovered on Linux using the 00-teensy.rules udev rules file. Is that the /dev/ttyACM0 and /dev/ttyACM1 files do not consistently point to the teensy monitor port (Serial) and the second USB port (SerialUSB1). It is much better to use the device nodes under /dev/serial/by-id. These are consistently named using the CDC interface numbers.

i.e. /dev/serial/by-id/usb-Teensyduino_Dual_Serial_12205920-if00 (Serial)
usb-Teensyduino_Dual_Serial_12205920-if02 (SerialUSB1)