The Hardiplank (maybe not called that now) is easy to work with, score and snap and used to be reasonable priced. Plus it will hold a finish as well as any other external surfaces which is usually down to the quality of paint and preparation.
https://www.bunnings.com.au/james-ha...board_p0716249
If you do go this way shop around for pricing, Bunnings are often far from the cheapest building supplies (especially metals).
Speaking of Bunnings, when I did a garden shed in my back yard utilising an old semi busted garden shed I was given I went to Bunnings and acquired the cover sheets from the packs of Colorbond steel fence panels free. They are often marked (tiny marks) and they throw them out. My entire front wall on the shed is done with the coloured fence panels and looks good. The local Bunnings no longer sells the stuff but other regions do.