useMipRadianceLayout property
Whether newly built environments store their prefiltered roughness
bands as mip levels of one equirect (sampled with hardware trilinear
textureLod) rather than the legacy vertically stacked band atlas.
Defaults to true, and applies only where the backend supports the
layout (see mipRadianceLayoutSupported).
The legacy layout remains supported for comparison and as the fallback. Each environment carries its own layout (detected from its texture), so flipping this affects only environments built afterwards.
Devices that report the layout as supported but sample every texture at its base mip (Adreno Vulkan, see https://github.com/flutter/flutter/issues/189965) do not need this turned off by hand; mipRadianceLayoutSupported measures the defect and keeps them on the atlas. Note the same clamp applies to every other mipmapped texture in the app, which no layout choice can work around.
Implementation
static bool useMipRadianceLayout = true;