I've reviewed about 50% of the translation. Used the french version as reference, side by side - so I was sorting the JSON keys to match the order in the French version to help out.
TBH I'm not sure if there is some more or less automated process in place to generate the missing strings to make this a little less error-prone, I may have missed that.
I've added a marker to help resume this work in the future.
Ideally this should be reviewed by a Catalan speaker, but I see none as a contributor to this repo.