How to download and setup contao-manager
Open terminal and run command
                                            git clone https://github.com/contao/contao-manager.git
                                        
                                        git clone is used to create a copy or clone of contao-manager 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 contao-manager https://github.com/contao/contao-manager/archive/master.zip
Or simply clone contao-manager with SSH
                                            [email protected]:contao/contao-manager.git                                    
                                    If you have some problems with contao-manager
You may open issue on contao-manager support forum (system) here: https://github.com/contao/contao-manager/issuesSimilar to contao-manager repositories
Here you may see contao-manager alternatives and analogs
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