It came up while producing this spreadsheet that it's unclear whether integer formats are ever filterable. @kvark surmised that they might be, in particular with Sampler Reduction Modes which allow samplers to reduces samples by min or max instead of by weighted average.

On Vulkan, at least, VK_EXT_sampler_filter_minmax has surprisingly widespread support - semi-recent AMD, NVIDIA, Intel, and Qualcomm (some Adreno 500+) all support it.