Use the texture arrays in order to use 24 block types. You can enable them by checking Use Texture Arrays in the foldout with the same name. Since HDRP is still in preview, I will wait for things to settle down first. I can't make Voxeland compatible with each and every HDRP change. I have plans for implementing low-poly look, but I'm pretty sure I will not make it soon. It's just a plan, I have not researched it to say if it is even possible (for now I can see a problem in vertex count, for instance).