You should still use dithering, even with modern palettes. You can absolutely see banding on undithered 24 bit images. 256 color levels per channel is barely ad

You should still use dithering, even with modern palettes. You can absolutely see banding on undithered 24 bit images. 256 color levels per channel is barely adequate, even when optimally allocating those levels perceptually (gamma correction is a poor man's approximation of this). Yes, dithering will increase the file size of a losslessly compressed image. That's because it contains more information. If you're sufficiently bothered by file size to degrade color accuracy, why are you using lossless compression to begin with? Dithering is an essential component of any digital signal processing pipeline, not some weird retro artifact.