If you're going to sell it, I wouldn't touch the software update mechanism at this point and maybe let the new buyer decide if they want it or not. there's no benefit to you to perform the update that I am aware of.
Thus far, my hangar of DJI drones includes two Mavic 2 Pros, a Mavic 2 Zoom, a Mavic Pro Platinum, two Mavic 1 Pros, two DJI Air 1s, a Mini 3, an Air 3, two Phantom 3 Standards, and a Phantom 3 Pro, all bought used on eBay, yet I still track...
So, I've been a user of Litchi since my Phantom 4 Pro. Used the waypoint flying a lot back then. Stopped flying for about 3 years and times had changed. New DJI consumer drones weren't able to fly waypoints except by "virtual sticks" which was...