Is there any way to use ternary axes in PGFplotsX.i had a stab at passing in raw latex arguments. But I guess it probably won’t be possible, since the choice of axis type is specified by choice of function eg Axis(args) or PolarAxis(args).
Pgfplots itself supports ternary axes, see tikz pgf - Draw a surface on a ternary diagram with pgfplots - TeX - LaTeX Stack Exchange for instance.
However I do not know if there is an interface to this in PGFplotsX.
Just adding a new instance similar to PGFPlotsX.jl/axislike.jl at 5145243095622247e8419b1fb4d0fa7d87ac627e · KristofferC/PGFPlotsX.jl · GitHub should be enough to support it properly.