How to download and setup InputSystem
Open terminal and run command
                                            git clone https://github.com/Unity-Technologies/InputSystem.git
                                        
                                        git clone is used to create a copy or clone of InputSystem repositories.
                                        You pass git clone a repository URL. it supports a few different network protocols and corresponding URL formats.
Also you may download zip file with InputSystem https://github.com/Unity-Technologies/InputSystem/archive/master.zip
Or simply clone InputSystem with SSH
                                            [email protected]:Unity-Technologies/InputSystem.git                                    
                                    If you have some problems with InputSystem
You may open issue on InputSystem support forum (system) here: https://github.com/Unity-Technologies/InputSystem/issuesSimilar to InputSystem repositories
Here you may see InputSystem alternatives and analogs
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