Plotting requires the python3-cairocffi package; without it installed,
gpu-mon fails ungracefully with something like:

*****

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_cairo.py", line 15, in <module>
    import cairo
ModuleNotFoundError: No module named 'cairo'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_cairo.py", line 21, in <module>
    import cairocffi as cairo
ModuleNotFoundError: No module named 'cairocffi'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/bin/gpu-plot", line 66, in <module>
    from matplotlib.backends.backend_gtk3cairo import FigureCanvasGTK3Cairo as FigureCanvas
  File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_gtk3cairo.py", line 6, in <module>
    from . import backend_cairo, backend_gtk3
  File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_cairo.py", line 23, in <module>
    raise ImportError(
ImportError: cairo backend requires that pycairo>=1.11.0 or cairocffiis installed
gpu-plot has closed
Quitting...

*****

It also requires the package python3-gi-cairo to work properly; without
it, the plotting screen opens but the plotting doesn't work, with many
copies of:

TypeError: Couldn't find foreign struct converter for 'cairo.Context'

being printed to the console.

I think that in addition, python3-gi is necessary for any GUI
functionality, and gnuplot is necessary for plotting.

These various dependencies should either be specified as either
recommends or at least suggests, and / or documented in the
documentation. My personal opinion is that both should be done.
ear Maintainer,

Hello,

I can confirm that at least python3-gi and libgtk-3-dev are required to
run gpu-mon. Since libgtk-3-dev brings a lot of other dependencies, it
may need some narrowing down.

Andrius