Saw this stunning work and was wondering if recreating a similar almost 2D painterly look was possible using shaderlab?
Yes
I mean, you mean in HLSL really, shaderlab these days means the Unity specific boilerplate that is used to write shaders for Unity.
A general painterly effect is probably easy (easy as in, you can probably find free or paid assets that do a style that looks kinda painterly), but if you want a specific and bespoke solution, it may need a lot of work.
Look up kuwahara filters. Or generally search for “painterly Unity”.
Or look up this game, I think they had some general info on how they did it somewhere:
