This is how to install Firefox via Homebrew:
brew install --cask firefox
But how to install the 'Firefox Developer edition'?
Everything I tried fails with 'Error: Cask '...' is unavailable: No Cask with this name exists.'
brew install --cask firefox-developer-edition
brew install --cask firefox-nightly
What's the correct command?
I've finally found a solution.
A lot of commands on the internet were outdated.
These 2 commands worked for me in 2022:
brew tap homebrew/cask-versions
brew install --cask firefox-developer-edition
If we go to homebrew repo in our Mac: /usr/local/Homebrew/Library/Taps/homebrew we see some folder like homebrew-core, homebrew-cask, homebrew-cask-fonts these files are what we get when we run :
brew search [formula or cask name]
When we do brew tap homebrew/cask-versions the casks files are cloned to our Homebrew repo. Since that, you may install an alternate cask that was not found before.
For more information, you may found it here.