I like to keep bigscreen mode primarily for games, but I find the desktop mode is not ideal when using from the TV even with a Steam Controller to use media streaming apps (Firefox progressive web apps, x86_64 Waydroid Aurora/F-Droid apps, and native Discover Store apps), and adjust other settings.
The answer to this pain-point is KDE Plasma Bigscreen. It has a Android TV like interface, and works well with controllers and remotes (FYI, the most reliable one I've tested, sold under a variety of brands). It's easy to switch between the regular Desktop Mode and Bigscreen from the sddm login screen, it's just a dropdown.
Someone recently gave it some much needed love to promote it to QT6, but it could use some additional contributors to bring it to a production grade environment, hopefully in time for the Steam Machine launch.
If you want the stable QT5 version, it is available with most distro package managers as:
plasma-bigscreen
But it does not work perfectly, there are known issues. I am staking my hopes in the next version.
If you want to try the latest on Arch-based systems like SteamOS without building from source, help with filing bugs (always appreciated), or contribute code, the QT6 version which I find more reliable in some ways, less in others, and some key associated dependencies are
plasma-bigscreen-git
plasma-remotecontrollers-git
qt6-virtualkeyboard
Else for Fedora-based Bazzite, or Debian-based distros like Mint, at least currently you need to build from source or help get the package into the testing branches.
One key thing that needs fixing is, since Mycroft voice control closed down, OVOS has continued the voice assistant codebase and skills library, but Bigscreen needs OVOS modules placed in where previously Mycroft was used. Definitely helpful for searching shows/movies with controllers/remotes that have a microphone.