I thought I could contribute to this thread but everything of value I know about this hymn has been posted already. So I only can add a bit of trivia:
This hymn was also used for more than a decade as a kind of common hymn for both Germanies when my Germany and their Germany formed a common team to compete in the Olympics. They couldn't agree on one of their respective hymns to be played in case of a gold medal. Beethoven was dead enough for a compromise. In addition to that you could sing their and our national anthem lyrics to this tune which left the respective opportunity to their and our gold medalists.

Wolfgang