person selects the one they want
i doubt he scrolls through 5600 items to select anything, unless it's the tiktok or instagram reels page.
So in my test of 6 thousand items with a height of 200dip per item, the list scrolls in release mode without visible problems. Just add the base panel and load the content via lazy loading, then you shouldn't have any performance problems when scrolling. The only thing that is stupid is the loading time when adding the 6000 thousand items, unfortunately there is nothing that can speed this up.
But I would recommend you to reload the site while scrolling, then you add the 1st 500 items on the 1st load, then the loading time is hardly noticeable and if your user is really so crazy and continues scrolling at 400 items, then you reload the next 200 items and so on and so on...