How to enable downloading from third party apps

Globuff wrote:

How am I able to download third party apps such as Firefox browser on Mac Air Catalina?

Is the device bound to Enterprise, mobile (MDM), active directory list ?

For a personal machine, ref:

Safely open apps on your Mac - Apple Support

If the app is not in the App Store, go to the General tab of "Security & Privacy" system preference and make sure it is set to allow apps that are not in the App Store.

As far as Firefox, go to the site and click the "Download Now" button.

https://www.mozilla.org/en-US/firefox/new/

Firefox is available to download here: https://www.mozilla.org/en-US/firefox/