Murdochs_Dad Thanks for reporting back!
Do I correctly understand that your journey would have been shorter if the "Unlocking the bootloader" section had begun with something like:
For this step, your device's screen must display a red warning triangle and the words "Fastboot Mode". You must not press the device's power button to activate the "Start" menu item, because the device must be paused in Fastboot mode for this installer to control it.