Despite it being in a FMLClientSetupEvent, RenderTypeLookup does not seem to be modifying any of the blocks' render types.
private void setup(final FMLClientSetupEvent event)
{
RenderTypeLookup.setRenderLayer(EarlyDaysRegistries.MOON_CREAM_BLOCK.get(), RenderType.getTranslucent());
}
public static final RegistryObject<Block> MOON_CREAM_BLOCK = BLOCKS.register("moon_cream_block",()->new SlimeBlock(AbstractBlock.Properties.create(Material.CLAY, MaterialColor.SAND).slipperiness(0.8F).sound(SoundType.SLIME).notSolid().variableOpacity()));
I have attempted this with other blocks as well with the same result.