Valve have their own VR headset, the Valve Index. Steam Link was previously a hardware dongle but has been replaced by android/smart TV apps with the same name.

I'm surprised Nvidia didn't attempt to partner with them rather than developing GeForce Now as a separate product, they could have taken advantage of Valve's developer relationship/client/store front and handled the actual running of the hardware, which Valve seems much less interested in.

Stadia on the other hand is just a demonstration of the level of hubris Google is capable of engaging in. They thought they could launch a brand new store with the twist that people would need to pay a subscription to continue playing the games they had bought and without the option of using your own hardware should you end up purchasing a capable machine.

They are partnered, it's just not exclusive.

https://partner.steamgames.com/doc/features/cloudgaming

Ah, that's interesting. I had assumed any partnership would have integrated with the desktop steam client rather than a third party app, although I can see the benefits of separating it out in terms of pricing/billing models.

With Steam Link requiring you to own a beefy computer it's not really a competitor to what Stadia offers (and I don't know anybody who was able to get good performance out of Steam Link).

VIVE is by HTC supporting SteamVR, but Valve has their own first-pary VR headset + controllers with the Index.

I was able to get latency down to 10-20ms using steam link over ethernet, it works great for pretty much everything. It might give you problems if you're playing at a very high level in csgo/fighting games, but for most people it's pretty solid.

You're a few years late. VIVE is a separate HTC headset now. Vavle Index is Valve's VR headset.

Steamlink has hardware is dead because it was bad. Steam controller is dead as well.

Steamlink now is an android app that might work and might not work on your device.