Yes, I know Light Level Overlay Reloaded exists (https://www.curseforge.com/minecraft/mc-mods/light-level-overlay-reloaded)

The reason why I'd want this back ported is to use the configurable nature of this mod, specifically the ability to change the level which the player is warned at. I'm backporting the light level 0 spawn functionality from 1.12.2 but this means it's now out of sync with LLOR, and there's no way to configure it.