the original release came with no subtitles and was only released in North America and Europe...so more than likely what you remember is from a fan patch which sadly is not compatible with this version of the game.

I wouldnt be shocked tho if sum of my info is incorrect lawl

BO1 was translated in a few languages. French for sure (I've seen that version), maybe also Japanese and German.

But GOG usually does what they can, and I doubt they were able to secure the French version too.

If I'm not wrong, at some point circa 2012-2015, the French version was actually pretty cheap online, due to a budget reissue. Maybe, if someone has bought it, they could try and supply the files to GOG and see if it can be added?

As Malek86 sayed, there was a version with French voices, it was on PC and Playstation.

I don't know how adding files to a released game on GOG works, i hope it is something possible
(and which could happen too).
But with the game barely coming to GOG, I hope and can't wait to see how the game can evolve, if it does.

Yes Fr version it is released for PC as well.
What is really looks missing - manuals. Again. But ENG ones can be found online for both PC and PS1 (ntsc?). And GOG not so responsive for now. Probably they can add first localised manuals, than localised versions?
Or not. They didnt add FR PC version for BO2. They do not add some games FR manuals as separate download like german ones. They do not add FR manual to one game.

Verok's OpenGL wrapper include some translations including some dub.

You can try to find French cue+bin disk image (from PC-redump set's, sometimes they appear on Internet Archive, its how i get PC NA eng version (although many sites provide it, im not sure how authentic that images and if it from U/C or UK) image).
(buying not an option for me... previously)

Bonjour Gewee,

"Verok's GL Wrapper & Patch" includes the french text and voicelines.
There's a topic regarding Veroks here on GOG: https://www.gog.com/forum/blood_omen_legacy_of_kain/veroks_gl_wrapper_patch

* Download "KainGL_1.73_MULTI11_FullPackage"
* Extract the downloaded files to the directory of your "Blood Omen: Legacy of Kain" folder, allow to overwrite files (no need to copy Setup.exe and Setup.dll, though)
* start Blood Omen
* Choose your language voiceline and text at the now appearing launcher

Rester bien
Z.