Lots of hobbyists use the ARM processor.

Most buy cheaper evaluation boards for their projects. The cheapest alternatives are small boards looking very much like a USB thumb drive, but besides the USB interface that allows you to power the processor and debug it, you also have one or more pin headers and maybe a special expansion connector. Many buys more traditional evaluation boards where the board is powered either through USB or a wall wart, and where you have a naked board with either four rubber feets or four stand offs as feets. Some people buy very high-end boards with audio, CAN, display, ...

But with the availability of gcc, you have access to a great compiler for free. And huge amounts of both documentation about processor and tools, and also published projects people have implemented.

More skilled users also often buys the chips and makes own PCB. Either really makes the boards themselves, or just sends the CAD material to a PCB manufacturer. With a bit of care, a number of surface-mount chips can be hand-soldered with very simple means.