I tried out the code with my receiver signal connected to A1 of the connector labelled "Analog In".
Two things now:
First, after downloading that code I get a single number on the serial monitor, followed by a stream of backwards question marks. The interesting thing is that I held the RC transmitter stick at each end, and in the middle, in turn, and after clicking download I got a number each time that is very close to what one would expect: ~1000, ~1500, ~2000.
But here is where my head explodes, and I guess this is the crux of my issue: On my Uno Rev3 schematic, the atmega pin 15 connects to the Digital/PWM connector pin labelled "9~" (verified on my ohmmeter); whereas the connector pin labelled "A1" connects to pin 24 on the atmega (again, verified on my ohmmeter).
How in Lucifer's name does this code seem to see a signal on pin15 which I thought was over on pin24?
My schematic is UNO-TH_Rev3e dated 06/03/19 12:33
Is there another UNO board which uses a QFP package? Is that what I have accidentally printed?