MIDI works with Linux because it’s a standard, but the keyboard might have other features or controls that are proprietary and only work with the original driver or software.

MIDI keyboards don’t make sound, they need a piece of software on the PC to do that… But you can also use them with a phone or tablet if you have the proper cable.

There are however keyboards with an included synthesizer and speaker, with multiple instruments and nice features like backing drums, rithms, arpeggios etc. These keyboards will need batteries or walk power, can make their own sound, but can also make MIDI codes.

These small keyboards are designed for portability so the keys are nothing like the piano keys you remember. They are lightweight and plasticky and sometimes not even full size. But they do often have velocity sensing, so you can play louder/quieter by pressing harder/softer.