How can I install a non-notarized application that is not in the App Store and not from a verified developer?

Question

Is there a possibility to install software that was not "notarized" for macOS Catalina? I have an application that worked on macOS Mojave but cannot be installed anymore on macOS Catalina. I think the developers must "notarize" this software. Checking with spctl -a -vv my.app confirmed that it is rejected.

1. What can an end user do about it to install it anyway until this process is finished?

Answer 1

In macOS 10.14 and 10.15, when an app fails to install because it hasn’t been notarized or is from an unidentified developer, it will appear in System Preferences > Security & Privacy, under the General tab. Click Open Anyway to confirm your intent to open or install the app.

See Safely open apps on your Mac from Apple Support.