My old mac running macOS Catalina 10.15.3 – thanks to Catalina Patcher
10 years old almost and running the latest macOS system. According to Mactracker it should only be capable of 10.13.6
Apple
Upgrading from Mac OS X 10.5 to 10.11 – Leopard to El Capitan
There are some extra considerations upgrading from Mac OS X 10.5 Leopard to 10.11 El Capitan.