I sent this newsletter out about a year ago; but it's worth repeating.
I do my main work, including this newsletter, on a 2002 Apple Mac G4, running Mac OS 9, with Javascript turned off. Big Brother finds it hard to hack; but they used to hack it when Javascript was on.
Mac OS 9, being incompatible with Intel computers, is the safest OS you can use. Next safe are middle-aged computers, such as Intel core i-5 Sandy Bridge (eg 2011 iMac).
My Intel Macs are 9-10 years old. More recent computers are designed to allow access to intelligence agencies, as Edward Snowden warned.
Forget about speed. Who wants a computer that runs at lightning speed, if it's compromised?