Any help with this would be nice, I cant find any answers online as to where this is referring to

You need to go to Rennes-le-Chateau - village near Toulouse - and talk to the village elder, he will show you the castle. But it's important to talk to him not through the village interface, but after heading to the center of the village.
After exploring the castle you'll find a book (it's in a chest in an extremely dark location inside the castle) which you'll have to read through view documents option in reports.

Then you'll have to head back to the temple limbrary during the night and find a secret passage behind the mural.

Finally, head to a cemetary in Rouen

There is a guid, but it's in russian
https://commando.com.ua/other/gaids/2810-gayd-po-prohozhdeniyu-mod-1429_la_guerre_de_cent_ans_edition_acier.html

Vinegar thank you so much for the help, seriously lmao

Where is the secret entrance in the cemetery? The crypt is a big empty room