I like Damon. I think he's chronically underrated. That said, on short notice against a guy like Chepe who has exceeded my expectations? I think he has his work cut out for him. Damon relies on using his veteran savvy to grind dudes out down the stretch but I'm not sure that'll work against Chepe, who has no shortage of experience himself and also doesn't really have the right weaknesses for Jackson to prey upon. Mariscal is by far the more comfortable striker of the two and has shown himself to be a competent grappler with excellent cardio.
Jackson's only hope is to control distance on the feet with his straight punches and kicks before ultimately initiating the grappling on his terms, winning the scrambles, and ending up on top long enough to control Mariscal and win rounds on that basis. However, while I'll be rooting for Damon to get it done, I sort of expect Chepe to pressure him relentlessly, rapidly scramble back to his feet if taken down (or at the very least survive any bad spots on the mat), threaten TDs of his own, and ultimately outhustle Jackson with his activity.