r57shell wrote retroarch cg-shader, that simulates PAL decoder artifacts and NES PAL/Dendy palette with help of feos, HardWareMan and NewRisingSun:
https://gist.github.com/realmonster/b89e63d4018eb5bbab62331c42acf9e7
Default shaders and presets paths:
\shaders_cg\crt\crt-royale-pal-r57shell.cgp
\shaders_cg\pal\pal-r57shell.cgp
\shaders_cg\pal\shaders\pal-r57shell.cg
\shaders_cg\pal\resources\nes_lut.png
Current version:
Shader can use RGB of all retroarch cores (not only NES!)
or nestopia RAW palette (more authentic PAL palette but more GPU-intensive)
For RAW mode you must uncomment line 70 of the
"shaders_cg\pal\shaders\pal-r57shell.cg"
#define USE_RAW
nestopia palette must be set to "RAW" if you're use this setting!
It's very GPU-intensive, so you can uncomment line 74:
#define USE_LUT
It’s less accurate, but much faster
pal-r57shell.cgp is clean preset
crt-royale-pal-r57shell.cgp is preset mixed with CRT Royale
Shader has many settings available via RetroArch UI