A Wagner documentary without Howard Goodall or Stephen Fry? Yes, it can be done.
Here's the earliest effort: Carl Fröhlich's 1913 silent movie The Life and Works of Richard Wagner. The series of reverential vignettes was put together to commemorate the 100th anniversary of the composer's birth.
Ideally it would have been accompanied by an orchestra playing Wagner's music at each showing, but the makers didn't want to stump up the required royalties. So they commissioned Giuseppe Becce to craft a Wagner-like score; close enough to sound like the real thing, but different enough to avoid legal retaliation. Becce bore such an uncanny resemblance to Wagner that he was drafted in to act the part of the composer as well.
There's no sound on the video above, so feel free to slam on some Daft Punk.
Finally, here's an oddity from 1982: Petr Ruttner's more fartsy than artsy Wagner e Venezia, with Orson Welles voicing the composer: