First of all, if you happen to have an Xbox/Playstation controller (or similar gamepad with two analog nubs) laying around you can try that first of all. That will not give very accurate control though. It is way better to use an actual RC transmitter.
If you are thinking of getting into the hobby more seriously my best advice would be to get a good RC transmitter right away which you can use to fly your real quads as well as practice on the simulator. For example the Taranis Q X7 is a popular radio which is good value for money I would say. It is highly likely that it will work as a joystick on your Linux machine, connected directly via USB, but you will have to try to know for sure if it works on your setup.