I started the course with a Sparkfun ESP32 Thing. After I selected the board with the board manager I had COM1 and COM3 to select from. I just received the DOIT ESP32 Devkit V1 board. After I select the DOIT board in the board manager I now have COM1 and COM4. I have tried both ports with every USB port on my computer, none of them work. I then switch back to the Sparkfun board and COM1/COM3 are back and it works fine. Any thoughts on what is going on?
It may be that the different boards require different drivers that hopefully do not conflict. I have one board that requires FTDI drivers and another that requires SLAB drivers. I can’t have them both plugged in at the same time. So first check your drivers. Then make sure you have both boards installed in your Arduino IDE. Make sure you have menu’s for both boards in your Tools->Boards menu. Then some boards have a special way to flash them by shorting a pin or holding down a button. Make sure you read everything you can about all the boards you have. It can be a pain to switch between different boards.
Note that what you see are virtual COM ports. The drivers take the USB port and make it look like a legacy serial port to the computer. In fact the FTDI adapter takes USB signals and actually converts them to serial for the board. I have to assume the onboard USB ports do the same thing.
Basically don’t worry about the COM Ports changing for different boards. That’s to be expected.