Thanks, found a related topic, experimented with .png/RGBD and faced the same issues as joie, terrible banding which I can’t seem to fix, but even if it’s fixable a .png is still pretty large and is no match for what webps/jpegs+gainmaps can offer in terms of compressed sizes and quality.
.env with webp compression (which you mentioned to be used as an environment map) gives a good compressed size and works well as a reflection texture, but it cannot be used as a lightmap.
I guess this could be something that is worth looking into for the devs