Just a general observation for other newbies like myself:
I plugged in my new mint condition Nano 33 BLE Sense board to my Ubuntu desktop via the USB connection. The Arduino IDE duly found the board and I confirmed that the port was correct (IDE didn’t append the board name initially). Still the code upload for Blink could not be completed by the IDE because it reported that the port (now correctly identified) didn’t have the correct board attached. No amount of plugging/unplugging could upload the Blink code to the Nano.
Then I tried the same operation on another board (viz. MKR1000) and everything went well with this board. Then I reconnected the Nano with the previous settings and voila everything worked flawlessly!
I know this note is lame and boring but it was yet another lesson for me to not rush into everything.