There are plenty of interesting apps from trustworthy developers which are not available on the Mac App Store and you might want to try them out. This tutorial explains how to easily run apps downloaded from unknown sources on your Mac.
How to run apps downloaded from unknown sources on MacOS?
To limit the risk of malware infections, the Gatekeeper feature of Mac OS X restrict the download and installation of applications to the Mac App Store and identified developers, namely to all the apps that follow Apple's PLA (Program License Agreement).
Open the Apple menu > System Preferences > Security & Privacy > General tab. Under Allow apps downloaded from select App Store and identified developers:
Download and install the app. To launch the app, press Ctrl and click on its icon > Open.