
What just happened? Facebook has stated that once the current stock of Oculus Rift S headsets dries up, the company won't be replenishing it with new units, therefore announcing its discontinuation. Moving forward, Facebook will focus on making the Oculus Quest 2 the first "mainstream" VR headset.
When Facebook launched the Lenovo-made Oculus Rift S in 2019, the VR headset was received with mixed feelings. As a successor of the original Rift from 2016, the Rift S improved in some areas, but in a few others, it was actually worse. For example, the Rift S features a total higher display resolution (2560x1440p vs 2160x1200p), but at the cost of a lower refresh rate (80Hz vs 90Hz).
Despite its flaws, the Oculus Rift S brought down the price for VR gaming with its $399 MSRP at launch. But now that the generally superior Oculus Quest 2 can be acquired for $299 (64GB model), there's no reason not to buy this one instead.
During Facebook's Q3 2020 earnings call, the company disclosed that the Quest 2 VR headset had received five times more pre-orders than the original Oculus Quest.

"Rift S is still available for sale currently in some channels around the world, but as we announced last year, we plan to stop selling Rift S in 2021," said a Facebook representative. "Generally speaking, as channels sell out of stock, they won’t be replenished moving forward."
As of writing, there's still stock of the Oculus Rift S on the official store and a few retailers such as Walmart and Micro Center . On the other hand, Microsoft, Lenovo, and Amazon do not carry it anymore.
Among the current crop of VR headsets there's the Oculus Quest 2 obviously, but there are other alternatives like the high-end Valve Index . Sony is also known to be developing a successor to the PlayStation VR and the rumored Apple VR headset.