I didn't find a working link on that website. But you got me inspired to search… 🙂

The BBC have a radio documentary on Metropolis' director Fritz Lang: https://www.bbc.co.uk/programmes/m0012s94

And through a German website ( https://www.avenita.net/roman-thea-von-harbou-metropolis-bbc-horspiel-dlf-doku/ ) I may have found the English radio drama at archive.org: https://ia800508.us.archive.org/30/items/00000008_202309/00000008.mp3