You can get an adapter board that will make it work with an M.2 SSD. I believe it’s only PCIe 2.0, so there’s no point putting a high end SSD in it unless you need a high write endurance. Any SSD will be a huge improvement over a hard drive.

Most Linux distros will run on it since it’s using a 64 bit Intel CPU. If you have the version with 4GB of RAM, you will need something very lightweight though. I would run Debian if I was going to use it as a server or Mint if I was going to use it as a desktop.