That's basically what I have been observing. I bought my Rift S a year ago. In that year, I haven't seen any updates pertaining to the Rift S. Atleast not according to any changelog I have seen. I only wish I had bought it recently so I could return it and put the money towards a better VR headset that might actually get support from the company that sells it. Facebook says its discontinuing the Rift S sometime this year. But from what I can tell, they stopped supporting it back at the end of 2019. Even though they are still selling them and the Rift S continues to be a top seller for them. How can a company justify selling a product that they have no intention of supporting? The Rift S could be so much better than it currently is. Unless something changes drastically I will never buy another Facebook product again.
A lot of updates that relate to the Quest will have implications for Rift as the Quest is effectively a Rift when using Link.
Oculus updates do tend to break things now and then which is annoying if it happens to an app you like to use... the latest beta update seems to make a difference to MS Flight Simulator white flashes so I have to revert back to the stable release... that affects both Quest in Link mode, and Rift alike. I'd say that will probably need joint work by Asobo and Oculus and may relate to OpenXR implementation.
If there are problems introduced for Rift users with an app, it's likely that the same problem occurs for Quest users using that app in Link mode. Problems like that are also more likely when the app is in early release stage, which it seems VR Chat is still in. This may just need an update from the apps developer... it can happen when any hardware related software change happens.
I'm using my Rift-S without any issues, other than having to revert to the stable release for Flight Sim, but as I say, that's an issue that will affect Quest in Link mode too.
First thing to try is opt into the beta program if you're not in it, or out of beta if you're in.... hope that works, if not let us know.
Intel 5820K OC@4Ghz, Titan X (Maxwell), 32GB Corsair Vengeance DDR4, ASRock X99 Taichi, Samsung 500Gb 960 Evo M.2, Corsair H100i v2 Cooler, Inateck KTU3FR-4P USB 3 card, Windows 10 Pro v20H2 (19042.867)