After installing Homebrew, run:
brew install adwaita-icon-theme enchant gobject-introspection gsettings-desktop-schemas gtk+3 gtk-mac-integration gtksourceview4 git pipx
pipx install git+https://github.com/jendrikseipp/rednotebook#egg=rednotebook[spellcheck]
pipx ensurepath
rednotebookTo create a shortcut to the application, in Automator (run as a shell script):
export LC_ALL=en_US.UTF-8 # change to a different language if needed
/Users/$(whoami)/.local/bin/rednotebookTo upgrade to the latest version, it is pipx upgrade rednotebook.
(Thanks to Peter Green for documenting these steps at https://gist.github.com/pmgreen/a1bf2c7015cb2a70d73e5e66bb84885e based on https://jarrousse.org/installing-rednotebook-from-source-on-mac-os-x/)