The main premise was that Discord takes human to Equestria's past. Before Nightmare Moon's banishment. And is now a changeling.

Falls in love, help make the town etc.

I forgot the name and now I can't find it.

Twisted fate?

7609317
Thank you.

This is the one.
It didn't have the changeling or human tag and that's why I couldn't find it.

7609317

7609323
Link to the story please? It sounds interesting

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Twisted Fate

Twisted fate is a great story, but it has not updated in a long time I'm sad to say. Another good story along this line is the substitute demon. https://www.fimfiction.net/story/255419/the-substitute-demon