There isn't a signal because PathFollow3D doesn't do anything on its own to move a Node. It just finds a point on the parent Path3D based on it's progress/progress_ratio value.

I would suggest wherever you are updating the PathFollow3D's progress, add a check for:

if path_follow.progress_ratio >= 1.0:
    # do something here, like emit a custom signal

I don't think it has anything to do with "politics". Blockchain / crypto is an area mostly focused on hype and marketing. So it's not surprising that their "hackathons" have little to no substance.