After examining the research on Liam O'Flaherty and his novel Famine, it seems there are no theater productions of any kind, including operas, adapted from the book. I am not sure what prompted your question, but after checking the link below, I can understand any confusion on this issue.
It seems that a man named John Dunne has directed a folk opera called Regent's Canal. He has also written a work entitled Famine, and he has adapted another of O'Flaherty's books, The Informer. He has not, however, created an opera from that title.
Aside from this connection, I find no indication that O'Flaherty's Famine has been produced anywhere in any form.