It depends on what you mean by "traditional" Catholic hymns. There is of course the French hymnal D'une même voix, several volumes of Chants notées, but you won't find much in terms for four part chorale style hymns or chants. There is a collection of Repertoire de Saint-Séverin that has more organ-based selections, including choral harmonizations in the style of Bach.
I used to direct a French Mass choir and have some transcriptions of familiar English hymns set in French. I will be happy to share if you message me privately.
(Side talk: Don't know if it were the fault of Google, but there seems very scarce Catholic resources in French. So as Youtube. Does setting English as the default language matter in the internet search?)
Thank you very much! By the way, does anyone know the name of the following hymn in French and its English equivalent? I heard it someday during Mass Recessional, but Youtube only shows the scout version of it.
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