Thanks for the advice
@i386!
Actually, I already have an order with WiredZone for a full chassis that includes BPN-SAS3-846EL1-N8, i.e. Supermicro CSE-846BE1C8-R1K23B4, and I was told by them that Supermicro doesn't have the chassis nor the backplane in stock.
They currently don't have any ETA for it, and I was told by a WiredZone representative on the phone that fulfilling orders for Supermicro chassis has been very challenging lately, with some customers still waiting after an order placed about 6 months ago.