If you own a Raspberry Pi, you can start several operating systems from a single boot medium. All you need is a micro SD card ...
You can build a media center with a Raspberry Pi fairly easily. Kodi is a local media center that can integrate with a broad range of internet sources, local network shares, NAS drives, cloud storage, ...
If you would like to create an open source Raspberry Pi powered alternative to the Apple TV you might be interested in a new project published by Jeff Geerling. That show how you can use a Pi 5 mini ...