I believe Canon has replaced the 5DSR with the Canon R5. The RF Mount is the future and Canon is discontinuing older EF Mount cameras and lenses.
FWIW, here is a link to the Canon US refurbished camera site, and the 5DsR listing. Out of stock right now, but you can select to get a notification when one comes available. This one is $1199
Shop Canon Refurbished EOS 5DS R Body | Canon U.S.A., Inc.
In January 2021, B&H had them on sale at $1499.00, which was when I bought one. This was the last of them. No one else had them. The Canon site every once in a while would have them as refurbished. B&H would get a few every month, eventually all of the supply dried up. This went on through 2021 and after that there were no more being sold. It was replaced by the R5.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.