The Happy Ending mod by Audemus' for Mass Effect Legendary Edition is now available on Nexus files. Link below.
The Happy Ending Mod, crazy name aside, cuts up content and dlc from the original games and creates an ending that is more in line with the original idea of the ending for Mass Effect, removing elements from the ending that fans were unhappy with and giving Sheppard a happy, or at least less catastrophic ending.
You can get the mod on Nexus Files but make sure to read the notes before doing so.