Image flashing

GUI tools

Balena Etcher

An open source cross-platform graphical program for flashing images onto SD cards and flash drives. It is simple and intuitive and even checks for defects after flashing by default. Nerds will be annoyed by the fact it's made with Electron.

Popsicle

A simple open source GTK application made by System76. No extra features, just helps you easily do what you need to do.

CLI tools

dd

Only use if you're already familiar with this tool.

Specialised

Raspberry Pi Imager

Probably the most convenient way of flashing a Raspberry Pi image onto an SD card. Includes helpful features such as setting up the wifi or the root password ahead of time. Offers many choices in terms of Linux distributions.