Hey Nnoggie,
Just a developer for Shadow & Light and was trying to find an issue a user is having conflicting with our 2 addons at the same time and while I was looking through your code base to see where the possible issue is I came across your ElvUI Skinning section in MythicDungeonTools.lua lines 4867-4885 on version 3.1.0
On line 4879 you reference colorAlpha variable but the reference is wrong. Should be ElvUI[1].db.tooltip.colorAlpha
I didnt test it or anything but feel free to test.

Both references seem to work on my end (No Shadow and Light)
Are you sure this is an issue on MDTs side?