Thanks for giving it a go, appreciate it. Understand too, you have other things to do than to test this.
For reference, it is not an ‘open anyway’ button. In the link you need to go to the section that shows the error message you were getting and the discussion there.
In System Settings > select the Privacy and Security tab > scroll down and you will see a Security heading and 2 radio buttons below the heading “Allow applications downloaded from” – one says App Store, the other says App Store and Identified Developers > check the radio button App Store and Identified Developers. This will then trigger a message when opening ‘suspect’ apps that will allow you to open them anyway.