I had problems using pyplot over ssh because it can assume there's a display and fail when it couldn't find one. Maybe this has changed. I use the OO interface. For example https://matplotlib.org/gallery/api/agg_oo_sgskip.html

Changing the plot backend should fix this.

  import matplotlib
  matplotlib.use('Agg')
  import matplotlib.pyplot as plt

https://stackoverflow.com/questions/2801882/generating-a-png...

I believe Agg is only for bitmap output. While there are probably backends that work with a headless system, I find the OO option much more flexible.

Agg works for all outputs. I use it in combination with OO over ssh all the time.