Other than Samson et Dalila they are uniformly 'unsung', and recordings are sparse or non-existent.
I agree, although
Henry VIII was recorded by Chant du Monde in 1991 (I think) and more recently Ediciones Singulares have released excellent recordings of
Proserpine and
Les Barbares, and I understand
Le timbre d'argent may follow. I think there was a 2008 recording of
Helene on the Melba label, if memory serves me right - don't know what it is like or if it is still available. So he is not doing too badly - at least of late.