AdvancedSettingViaSerial1: Error 'Serial1'was not declared in this scope'

[terrypin999]

On compile to my UNO I get 'Serial1'was not declared in this scope'. That string appears nowhere in the code.

[terrypin999]

I posted yesterday in the Arduino forum and had the reply:
"well that's because you don't run it on an Arduino where Serial1 exists (like the MEGA)."

My reply just now:
"Thanks, that clearly explains that point. However it’s clearly stated in the introductory comments that the sketch was tested on the UNO."

All those examples carry the same comments which I now see were by DfRobot's Angelo qiao five years ago, and clearly were not edited.