Valve updated their article about when the Steam Machine/Controller/Frame will ship.
Previous message:
We hope to ship in 2026, but as we shared recently, memory and storage shortages have created challenges for us. We’ll share updates publicly when we finalize our plans!
New message:
We shared recently that there have been challenges with memory and storage shortages, but we will be shipping all three products this year. More updates will be shared as we finalize our plans.
You can use any controller with it, though. I bet there will be a lot of people who love their Xbox, PS5 or Gamesir controller and just want to stick with that to save $50 or whatever the price difference will be.