"There is not a native app on Steam deck today," said Andrew Fear, GFN boss, back in January. "Use a Chromium browser to make it work. I would say that both Nvidia and Valve, I think we're both interested in making [GeForce Now on Steam Deck] better. But we don't have any announcements on a native app coming to Steam."
You're describing GeForce experience.
GeForce Now is the cloud gaming service.
Oh! I had never heard of that. My mistake. Is that different than Moonlight/Sunshine game steaming? Does it stream from the internet like (the now defunct) Stadia rather than a local machine?