And do you know whether they all work? I came across a neat video prepared by amateur radio operator W2AEW, a 10-minute tutorial on checking components. The video gives an example of performing simple ...

Now [jgpeiro] has made one which is light years ahead of the toy kits, using a Raspberry Pi Pico, a 100 MHz ADC, and an effort to design a better input circuit.

This particular video uses the Z-axis input on an analog oscilloscope. The input is composite video that's used to create X and Y sawtooth ramp signals from the vertical and horizontal sync pulses.