"我和朋友明年会去法国" should also be accepted. Time words can be placed at the beginning of a sentence or right after the subject. Please see:

https://resources.allsetlearning.com/chinese/grammar/Chinese_word_order

"Time words, the WHEN part of a sentence, have a special place in Chinese. They usually come at the beginning of a sentence, right after the subject."

朋友和我明年~ 为什么不行啊~

Can you say 我和朋友明年会去法国？

I've just started the course and I find it weird that I, a sinologist, am unable to pass the 4th big test because of forced unnatural grammar :/

I'm finding the Chinese course on Duolingo pretty stupid because grammar is quite flexible in Chinese but Duolingo forces you to phrase sentences a certain way.

As a native speaker of the Chinese language, I can tell you that "我和朋友明年会去法国" is totally acceptable and word order is not even that important in the Chinese language, unlike certain languages such as German. Duolingo really needs to review the answers in the Chinese course more often.