The text seems to imply the embedded video of Drake singing River Man is the self recorded demo version from 1968, but it is from a Tim Pope 2004 video containing a "remastered" version (with added sound effects and goodness knows what else) of the Island Records album version on Five Leaves Left

For anyone interested, the versions are:

Demo version (cambridge version): https://www.youtube.com/watch?v=6QDxEGmb0-U

Album version: https://www.youtube.com/watch?v=HQ9JBwuO128

Tim Pope video version: https://www.youtube.com/playlist?list=PL0QFDUXn1p9SLRMz623qn...

Bonus John Peel session version: https://www.youtube.com/watch?v=l2bbaa4qAh0