Slicers on linux work just fine. At least the ones I’ve tried. With CAD you have a bit limited options. FreeCAD is fine if you need a new knob for your appliance or something relatively simple. OpenSCAD can do pretty wild things but learning curve for it is pretty steep. And then there’s browser based cads but they tend to have monthly subscription. Plus of course Blender, but I wouldn’t count that as CAD-software and that if something needs time and effort to learn.