Fountain Mode is compatible with Emacs version 24.4 and later.
For Emacs versions older than 26.1, there is a bug in the outline
library. This will be automatically patched provided
fountain-patch-emacs-bugs is non-nil and Emacs is installed with
its Elisp source files.
For Emacs versions older than 25.1, the seq library will need to
be installed. If you install using the Emacs package management system,
seq will be installed automatically.