Harry Bloomfield wrote:
So far as I could tell, I have installed a driver for it in W10, and it
ought to have a port called 'Arduino', but it doesn't. Device Manager
shows in ports 'USB Serial Port (COM3) which appears and disappears as
the Arduino is plugged in.

Following the procedure described to install the proper driver, it
crashes W10 and forces a reboot.

I think your drivers are confused. Your board has an FTDI USB-serial chip
(FT232) - you can get the VCP drivers from he
https://www.ftdichip.com/FTDrivers.htm

Once you have the driver, it should show up as the COM port in Device
Manager, and stay there when plugged in. Then you go into the Arduino
software and tell it your board is plugged in on COM3 (or whatever number).

I don't know what the 'Arduino' in Device Manager is, I've not seen that
before. There are fake FT232 chips and, depending on where your board came
from, you might have one of those. They don't work properly.
https://forum.arduino.cc/index.php?topic=274359.0

Theo