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