Hi Hobbitses, welcome to the forum, glad you made it over here from BGG.
All the expansion components are language independent, which means you can buy from anywhere. It's only the rules that will be in the language of origin.
The Big Box 2021 rules aren't available in English yet, but all of the expansions have been previously released, in fact it's identical to the last big box. The artwork has been slightly refreshed, and perhaps there's some minor rule tweaks.
https://www.zmangames.com/en/products/carcassonne-big-box/Don't rush to order the French one, unless you're French, or need it in time for Christmas. The German edition is releasing in the next week or so. You'll have more retailers to choose from. I suspect the English edition from Zman won't rear it's head until mid 2022.
Also, where are you based, local Carcassonne players may be able to recommend the best places to order from.