If you aren't looking for a total world overhaul, some "Noir" packs focus purely on the user interface (UI) to reduce eye strain:
Predominantly grayscale, though newer blocks may still appear in color. Noir Texture Pack.7z
A minimalist Bedrock pack from NoierUi - Minecraft Bedrock Texture Packs that reworks equipment like Netherite and Diamond tools into a cleaner, dark style. How to Install the .7z/.zip File If you aren't looking for a total world
Available on the Marketplace for approximately 830 Minecoins . 2. Create: Noir (Java Edition) Noir Texture Pack.7z