Rivard has always been advertising a discount. I don't know anything about that dealership or if anyone has actually been able to buy at those prices.
The other dealership that has been advertising a discount (supplier pricing) is Robideaux Motors in Idaho. I had an order with them for 9 months, never got an allocation and ended up finding what I wanted elsewhere. I got my deposit back, but they never cancelled the order. It ended up getting allocated, built and delivered to Robideaux 17 months after I placed the order. I know this because my contact information was still attached to the order number so I got the e-mail notifications about its build and delivery status. They are nice people and some other forum members have had their orders built and delivered, but they aren't high volume and there's no knowing how long you'll wait if you place an order with them.
Other than that, some forum members have been able to get supplier pricing, but it usually seems they either A) Have a long relationship with that dealership or B) Live in the Michigan area where there are a TON of GM employees/family and the expectation is that most dealerships in that area will always honor those discounts.
These rigs don't sit very long so there really is no incentive to offer discounts. Expect MSRP - you can always bring up a discount, but don't be surprised if they don't budge.