Framebuffer fetch shader in Unity

fbfetch.shader

#include "UnityCG.cginc"
#pragma vertex vert
#pragma fragment frag
// in practice: only compile for gles2,gles3,metal
#pragma only_renderers framebufferfetch

struct appdata_t {
	float4 vertex : POSITION;
	float2 texcoord : TEXCOORD0;
};

struct v2f {
	float4 vertex : SV_POSITION;
	fixed4 color : TEXCOORD0;
};

v2f vert (appdata_t v)
{
	v2f o;
	o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
	o.color.rg = v.texcoord*4.0;
	o.color.ba = 0;
	return o;
}

void frag (v2f i, inout fixed4 ocol : SV_Target)
{
	i.color = frac(i.color);
	ocol.rg = i.color.rg;
	ocol.b *= 1.5;
}

Does Vulkan Support it?

I think only Apple hardware supports it as-is (so basically "Metal only" these days). On Vulkan you'd want to use "sub-pass attachments" or some stuff like that to achieve something similar, but then I know almost nothing about Vulkan.