RetroArch already has excellent AI-free shaders for DMG-style, MGB-style, Gameboy Light-style looks for black and white, dot matrix games, and a GBC-style look for an excellent, all around LCD shader, along with countless excellent CRT shaders and presets.

You can find them in the shaders_slang/handheld folder.

DMG: gameboy.slangp

MGB: gameboy-pocket.slangp

Gameboy Light: gameboy-light.slangp

GBC/general LCD shader: authentic_gbc.slangp