Steamlink was abandoned too early, I had one and it was frustrating but was 100x easier than other gamecasting options
they moved to app-based, but then smartTVs and androidTV kept rugpulling them, and in the end they sorta needed it to not even attempt to work over 2.4GHz wifi, leading to them just dropping development of it.
The in-home streaming market is WAAAYYYY bigger than people think (look at Playstation Portal), being able to easily cast to a 2nd screen/device elsewhere in your house. Steam needs to simplify this, and them not releasing a Steam-branded TVstick is a little disappointing. If the SteamCube is super portable and boots fast (like the deck) it will work, you can technically do in-home streaming using just the deck currently but it's not ideal because pairing an external controller and non-natively scaling is kinda underbaked.
In home streaming between devices is definitly huge, idk about casting to a TV. I dont think a firestick adjacent device would be enough to run anything meaningful smoothly, but i could definitely be wrong. I think one of my TVs had a Steam app, but it was so dog shit I cant tell you what it actually did, maybe im just making that up. Also while I dont really like controllers, i think theyre just better in some games. My only wish is that if I'm going to spend 70 dollars or more on a controller it was actually made for the hands of a normal human and not like a tiny baby 12 year old.