We use lossy texture compression where available on iOS using MTLTextureCompressionTypeLossy. This is typically only available on newer iOS GPUs (A15 Bionic and above I believe). However, the memory savings are massive the visual differences unnoticeable.

We should opt into using the same kind of texture compression on Vulkan on Android. Universal support for this, like on iOS, is absent. But it is available on certain ARM Mali GPUs. ARM calls this ARM Fixed-Rate Compression (AFRC) and it available to opt-in via the VK_EXT_image_compression_control extension. This extension isn't widely available ~3% on vulkan.gpuinfo.org on Android as of this writing. But, notably, it is available on all Pixels 6 and above and may be the norm moving forward on higher end ARM Mali devices.

Unlike Metal, AFRC allows you to pick the compression ratio. Moving from a 2x to a whopping 4x ratio. More information about this and other Vulkan optimizations is in a recent talk about Vulkan best-practices for mobile.