According to the Vulkan spec (https://www.khronos.org/registry/vulkan/specs/1.2-extensions/html/vkspec.html#primsrast-sampleshadin...) sample shading should be enabled when ``SampleID or SamplePosition are used in the shaders. It's not the case and work fine with other GPU vendors, but not on AMD GPUs (tested on a RX 6800). Eg. gl_SampleID incorrectly returns 0 all the time.
Getting a repro should be straightforward so I won't provide any.
A bit related to https://community.amd.com/t5/opengl-vulkan/msaa-with-sample-shading-disabled-does-not-work-on-navi-w...