Emacs is available for Linux, MacOSX and Windows. The Spacemacs Readme suggested ways to install Emacs
Minimum Emacs Version - 26.3
sudo apt-get install emacs
Ubuntu Personal Package Archives
If the Emacs version you want is not available, add the Personal Package Archive from the Ubuntu Emacs Team.
Try the latest nightly builds of Emacs using the
emacs-snapshot package, although be aware that some things may break. You can install
emacs-snapshot packages at the same time, calling
emacs-snapshot to run the respective versions of Emacs.
For a self-contained install, download Emacs 26.3 or later from the Emacs for OSX website.
brew cask install emacs
Download Emacs-26.3 from the GNU repository and extract the zip file to
Access to common Unix tools
Command line tools, such as
diff, are used by Emacs. To have these command line tools available in Windows, install Emacs as above but then run emacs from a Unix shell such as GitBash.