The dropdown box reports various wrong conditions:
In this case I was using the IDE with a NodeMCU processor on COM8. I opened a NEW sketch (the one you see in this screen shot) Selected a Arduino Pro Mini. Did not chose a COM port as the board was not yet connected.
The program compiled successfully, yet the dropdown box shows a NodeMCU with no port is checked.
When I was working with the NodeMCU and it was disconnected after being connected, the port would sometimes default to COM1 then when I selected the correct port COM8 the dropdown would shot both configurations checked:
The "at undefined undefined" looks very significant to me.
Are you able to reproduce this repeatedly, or did it only happen once?
How did you select the boards? The Arduino IDE 2.x offers multiple ways to select a board. You can do it the traditional way via the Tools > Board menu, via that "board selector" dropdown menu shown in your first screenshot if the board has been associated with a port, or via the "Select other board and port..." dialog accessible from the "board selector" menu.
This bug is being tracked by the Arduino IDE developers here:
Unfortunately, I have not managed to find a process I can follow to reliably put the IDE into this bugged state. Have you found a way to do that? If so, I think that would be very helpful to the developers in the investigation and fix.
I will try to find a sequence that causes this to happen. It seems to be when I change processors without shutting down the IDE. I've been working with a ProMini and a NodeMCU. They each have a different COM. My computer has one hardware serial port (COM1).
It happens regularly but not always the same symptoms. I play some and add to this post (if that is best).
