@Ralph_Not_Lauren
I have used a serial monitor with a "ESP Link" USB/UART adapter and the above code. This adapter is labelled from the other viewpoint, so pin 3 goes to the pin labelled RXD and 4 goes to TXD. Ground should also be connected to improve reliability.
The example supplied with the "MH-ET Live Tiny88(16.00MHz)" core uses the default Serial device so I tried it with that code, same setup, and that worked just fine as well. So it appears that 3 and 4 are the default UART pins for that core.
With the ATTiny88 plugged into one USB port, the ESP Link adapter plugged into another, and the Reset button to invoke the bootloader, downloading and debugging is nearly as convenient as any other Arduino.
I still get the message about a failure to recognise the USB device, but I figure that is just Windows complaining about the port getting stolen for the loader, and ignore it.