This article is about macOS High Sierra – but the newer versions are working the same way.
There is a way to install newer versions of macOS on older unsupported Macs. The tool is called „macOS High Sierra Patcher“ and can be found on this website with instructions:
Personally, I did it on my Mac Pro ’08 (MacPro3,1), which officially supports only OS X 10.11 „El Capitan“. With the „macOS High Sierra Patcher“ I managed to install the latest macOS (10.13). Now I have Siri and many other new features on this computer. The usage is still very good.
El Capitan On Unsupported Mac
Dosdude High Sierra Patcher
El Capitan Patcher Tool. OS X El Capitan on Unsupported Macs macOS Extractor, OS X Patcher, and MacPostFactor are apps that guide you through patching and installing OS X El Capitan (10.11), Yosemite (10.10), Mavericks (10.9), or Mountain Lion (10.8) on your older Mac. Developed by Kelian Dumarais (MLforAll) Verison 2.0.1. MacOS Extractor is a legacy Application that assists you in install OS X 10.8-10.11 on your Unsupported Mac. By using this patching software on your Unsupported Mac, you can enjoy the various features and added security that modern Macs have.