Square Axis Units
Axis rules can be put in place which force the vertical scale (units per pixel) to match the horizontal scale so circles always appear as circles and not stretched ellipses.
ScottPlot.Plot myPlot = new();
myPlot.Add.Circle(0, 0, 10);
// force pixels to have a 1:1 scale ratio
myPlot.Axes.SquareUnits();
// even if you try to "stretch" the axis, it will adjust the axis limits automatically
myPlot.Axes.SetLimits(-10, 10, -20, 20);
myPlot.SavePng("demo.png", 400, 300);
This recipe is one of many in the Axis and Ticks category