Linux

Seems like Mint is the consensus and I don't disagree. Just some things to consider when choosing:

1. Desktop Environment/Window Manager (DE/WM) this is the software responsible for displaying your desktop and managing the opening and closing of graphical windows. Window managers are very bare-bones and might offer an experience significantly different than Windows. (See tiling WMs). Desktop environments do the same and more, and are often bundled with launchers and useful default programs like terminals and editors.

2. Package manager. Package managers are responsible for managing your installed software. There are a variety of options, and distros typically will choose one as their default. Pacman for Arch, Aptitude for Debian, RPM for RedHat, and others. These are mostly interchangeable for the end user, but each has slightly different commands and frontends. So just be aware there will be a bit of an extra learning curve moving from a distro that uses one to a distro that uses another.

3. Release cycle. Different distros offer different styles of releasing updates. Ubuntu and Debian periodically release updates in a cycle with major and minor releases. Some releases are marked for long term support and others marked as short term. Upgrading releases has been hit or miss for me, so I prefer rolling release distros. These distros don't distinguish major releases and simply upgrade in place. Each has it's own advantages, just be mindful of how often you will have to upgrade.