There seems to be a secondary deal going on in this thread when purchased on Samsung.com And a list of applicable discounts that are combining.
Make a new Samsung.com account
Preorder FE Unlocked (not tied to carrier or factoing carrier discounts) $699
PM to Bestbuy either via chat with them issuing you a $100 code via chat or email OR pm after shipped via screenshots and receive a $100 refund.
(Amazon has raised the price to $699 so they are no longer eligible for PM)
Use either Ed, 1st Responder or Affiliate discount on welcome screen, EDU email not required
Generate your own referral code on a different Samung account by going to referrals.
Apply trade in phone credit if applicable
Use a click thru site for 3% Cashback (such as RakU10)
Use Discover 5% Cashback with PP purchase (exp 10-01)
Use Chase 5% Cashback with PP (after 10-01)
Samsung is currently offering a $70 store credit, you do not have to use it at time of purchase. Ymmv but you may see a banner for a $90 credit instead if ordering on a Samsung device. This happened for me.
After you place order You can click on the "Cancel Order" button and choose reason (I personally chose would not arrive in time) then a button will come up to offer a 10% discount and choose accept.
All discounts should apply together. Per previous recent Samsung.com deals PM after shipping seems a given but YMMV