Forthcoming from Bru Zane:
https://www.prestomusic.com/classical/products/9313661--franck-complete-songs-and-duets
Interesting. Not at all familiar with Franck's songs... may have to indulge.
Hungaroton released a selection of his songs a few years ago, some of which can be heard on Naxos Music Library (eg L'émir de Bengador (1842-3) - which can also be heard in a recording on Brilliant Classics.)