Luke Skywalker would have a fruitful and working Jedi Academy, and the galaxy would mostly be at peace.
Luke would have a kick-ass opening scene, with the force being used to move immense objects and remove enemies at ease - leaving the audience at awe from when we first saw him. Now our hero is not just that; he’s also the most powerful being in the galaxy.
He would have a follow-up scene with Han and Leia, at his academy and upon his return, with a funny but also heartfelt conversation. They have been visiting Luke (and their son, Ben) for years and watched the Academy and their son thrive. They are happily married and run some sort of business together, whatever it may be.
Then, after some great character development and also introduction of new and likeable characters, we would be introduced to rumours of a black hole in the galaxy; giant ships having been seen flying in and out. Ships not of the modern age.
The black hole is revealed to be some sort of timelapse portal to The Old Republic era, with the Dark Lord of the Sith having created this dark hole with all their might and power to sometime return if the power of the Sith is threatened (be it by their extinction).
This is the sole conflict, and the first film would end with The Dark Sith Lord (Revan? Malek? Someone new?) turning Ben into his apprentice, killing Han and Chewbacca to raise the stakes and leaving Luke with a facial expression in a close-up that can only mean one thing; his father’s anger is still in his veins, and what will Luke do with this power and conflict as he will surely avenge his fallen friend’s legacy and try to save his nephew Ben from The Dark Side?