aleveltech yeah, that would be because it's a GitHub fork and not an actual repository. Unfortunately it seems the author of this fork has not created a discussion here either, so this might indicate their fork is not ready for use.
I am the author of the original Flagrow Telegram extension, but this extension has been abandoned and there is currently no plan to update it, so I can't help. It would be up to the author of the fork to officially publish their version as a replacement if they wish so.
