Add TextureRect to your scene, set expand to to true and make your TextureRect fill whole screen. Then set texture of this rect to any image (even default icon.png will work). After it, add material to this TextureRect and add next shader:
shader_type canvas_item;
void fragment() {
vec4 color = texture(SCREEN_TEXTURE, SCREEN_UV, SCREEN_UV.x * 3.0);
COLOR = color;
}
Here 3.0 is the blur factor: the bigger this value is, the blurrier image will become on right side of the screen. This should give you result similar to your image.
P.S. Here's the link to the image in this post (got it from page source using inspect tool) https://drive.google.com/file/d/13pLOPcojFHA_pUkCASTRX5AUit5l2znt/preview