Pop_OS!, a popular Linux distribution, is writing a new desktop environment. A desktop environment is basically the functionality of the desktop, think the taskbar and window snapping, etc. on Windows and the dock and top bar on macOS. A desktop environment also comes with its own set of apps, like how Windows comes with Explorer and Task Manager.
My dad got me a Raspberry Pi for my 10th birthday. I used Ubuntu Mate 16.04 and was amazed by the customizability. Switched my laptop in 2019, never looked back.
Steam offline mode doesn't need to phone home, you can use steam entire offline as long as you're not downloading any new games or updating