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