But here is the paradox: The 2016 installer is actually more secure than a pirated copy of Office 2026. Why? Because it doesn't have a live network connection to a telemetry server that can be exploited.
Given the age and lack of security updates, consider: microsoft-office-2016-installer.pkg
Modern macOS security (Gatekeeper) may block the installer if it does not recognize the developer's current signature. But here is the paradox: The 2016 installer