Highly recommend Linux Mint, Ubuntu or Fedora for your main desktop distro when coming from Windows. They have an extremely wide user base, huge list of easily installed and compatible software (like, search for it in the built in software center app and one click download and install it, instead of having to use the command line or build from source), and will definitely be the easiest to triage issues in/find answers online for.

One big consideration is driver support. Yes you should be able to set up all drivers you need on basically any Linux distro, but the three above basically are designed to do it for you, including the proprietary drivers needed for certain web content with annoying DRM, and for NVidia graphics cards. There is an open source driver for NVidia, but my understanding is that the proprietary one has way better compatibility and performance (this is purely hearsay, as I have an AMD card, so I'm not speaking from experience).

Others have mentioned the things about SteamOS being made for the one specific handheld, which is true. It boots straight into the gaming handheld mode by default, so if you wanted to see the desktop you'd have to load that, then go to the menu and select "switch to desktop mode" every time you boot.

Plus you can just get that exact same gaming mode UI on any desktop with steam installed by going into the menu and selecting it or hitting the home/Xbox/PlayStation button on a connected controller when steam is open.