Installing from .deb files in macOS Catalina
As far I know, a .deb file is a packaged software installer for Debian Linux (and its derivatives.) 

If you want to install it, you're out of luck. I don't think there is anyway to install .deb packages on OS X.

However, we can unpack a .deb file on Mac OS X without installing it. 

If you use Xcode, a utility called ar is installed. You can run the following command:

ar -x path/to/filename.deb


Alternatively, you could use Homebrew to install the dpkg utility which has many more options to work against .deb files.

dpkg -c path/to/filename.deb