Desktop

There are two parts to choosing a good Desktop: hardware and software.

Hardware

X86-64 is a 64 bit architecture predominantly made by Intel and AMD. It is most commonly used in laptops, desktops, and servers. The author favours AMD where possible.

In general any second-hand desktop newer than ten years old will be powerful enough for light browsing, office work, and communications. Backmarket is reliable.

Software

There are many compute operating systems available but only one is free, privacy respecting, and has sufficient hardware support to run on almost anything: GNU Linux. Other excellent alternatives are FreeBSD, NetBSD, and OpenBSD.

There are many different varieties of Linux, known as distributions. Linux Mint is commonly recommended.