Since I just got myself an ST7920 128x64 LCD display, I had a go at building Mirko Pavleski's oscilloscope, following the instructions at https://create.arduino.cc/projecthub/mircemk/diy-10hz-50khz-oscilloscope-on-128x64-lcd-display-52ecfe.

There is a couple of adjustments that need to be made, as outlined in goldenxxxl's comment on the page, but after that it works beautifully.

In this video I am trying it out with my Korg MS-10, demonstrating triangle, sawtooth and pulse waveforms.