Own a gamepad / controller that has a built in gyroscope? Using it for first-person shooters might be about to get better for you with JoyShockMapper and Steam Input for Steam users.
What's all this then? Well, JoyShockMapper is an open source project (MIT license) from developer Jibb Smart available on GitHub that gives you new ways to use controllers like the PlayStation DualShock 4, Nintendo Switch JoyCons, and Nintendo Switch Pro Controller because of the gyro inside. It can give you much finer aiming than just using the right stick by itself and it sounds awesome.
Have a look at Smart giving it all a demo in the below video:
JoyShockMapper itself was previously only supported on Windows but as of a few days ago, a developer mentioned that it should now work on Linux too! They're planning to provide Linux builds soon, once they get the flow right on the dev side to enable that but you can manually compile it all together yourself to test if you wish.
On that subject, Valve recently put out a fresh Steam Beta on July 17 which upgraded Steam Input with an added implementation of Jibb Smart’s Flick Stick too. Valve also said they managed to lower the CPU hit on some Steam Input API calls. On the Linux side, the Steam Beta should also now actually do something when you hit the "STOP" button on 'non-Steamworks titles'.