Great job on this mod, I was asking for this functionality on the forums years ago, very happy to see you made it a reality!
And its surprising, as I was told numerous times, how problematic it is... and than you just... release the finished mod
I scan the area for light sources and calculate the lighting manually.
It's not pinpoint accurate, but it should be reasonably efficient and flexible.
I'm still not certain what formula Unity uses for light fall-off values, I just concocted my own.
I have noticed a bug with light bleeding through walls sometimes, I'll have to put out a fix for that.