To make Fred.app work on macOS versions before Tahoe you will need LLVM 20+.
You can grab it either through Homebrew (easiest, brew install llvm), from GitHub
(https://github.com/llvm/llvm-project/releases) or from their official site
(https://releases.llvm.org/)
Note down the path where you installed it. In case of Homebrew you can run brew --prefix llvm to
get the path.
Then continue to download Fred.dmg from Dropbox, and move the Fred.app into a user folder (i.e. ~/Downloads)