I have 2020 w/ 47k that has this same clunky rattle that you described, super annoying! I have only put about 2k on it from 1st owner & did not notice this when I test drove, but the roads were smoother than where I'm at I guess. It rides great on highway/smooth roads, but happens on side streets that are crap condition.
Once I noticed this, I hit up the forum & did some homework - removed all skid plates, tightened all suspension components, checked rod ends, ball joints, sway bar, shock tower bolts, etc. Basically everything I could access, I put a wrench on & nothing came up loose/worn IMO. I drove it afterwards w/ the skid plates off & was only very slightly better (some of the bolts/nutserts on the plates were marginal, so replaced them). While going through the underside, no signs of heavy abuse, looks very clean. I looked at a few others that were so bad, I didn't bother to test drive.
I thought for sure it was a loose spare tire, but not that either...
I spoke w/ the dealer & would like to have them look at it before the 60k warranty is up, but I am not confident they will find anything & feel that will be a waste of $$$.
Curious on what you find atayl5513 as it sounds like we are chasing the same issue