Why brew install returns "cask is unavailable" on terminal if homebrew's website shows a different information?

Question

I am trying to install this software called Next browser. There is a page about it on brew.sh.

When I run the command displayed on homebrew's webpage on my Ubuntu 18.04 LTS terminal:

$ brew install --cask next

I get the following error message:

Updating Homebrew...
Error: Cask 'next' is unavailable: No Cask with this name exists.

Observation, I am able to sucessfully install other packages like:

brew install hello

Why is this happening?

Is there a way to fix this?

Answer 1

Casks install are only available on macOS because they install macOS-specific .app files.

This probably explain the error you get, although it could be made clearer.