I see that MainWP Links Manager is now unavailable to download.
There is any similar extension or plugin to manage backlinks?
We don’t currently have anything.
Thanks for your reply @dennis.
Why did you retire from this extension? Can I still download it not officially? 
Links Manager extension has been retired a long long time ago.
It actually never made into version 2, so since the code is very much outdated, it can’t be activated on the current MainWP Dashboard version.
@bogdan thank you for your reply.
Maybe users with experience can prompt, how to manage link building between sites into the network?