The original text of Claudine à l'école begins with:
Je m'appelle Claudine, j'habite Montigny ; j'y suis née en 1884 ; probablement je n'y mourrai pas.
From what I can see from the trailer, the English-language biopic of Colette quotes this part of the novel, translating it as: My name is Claudine. I live in Montigny. I shall probably not die there. For some reason, the French dub in turn translates this part of the script with:
Je m'appelle Claudine. J'habite à Montigny. Probablement que je n'y mourrai pas.
Alongside the omission of j'y suis née en 1884, which I thought ruined the symmetry of the original text, this addition of que bothered me. I knew of adverbs like peut-être which require inversion or the conjunction que when used at the beginning of a sentence, but I had not known probablement to be one. Checking TLFi, I found that I was likely wrong. At the same time, Google Ngram viewer suggests that probablement je was more common than probablement que je until very recently. It is possible, however, that those instances of probablement je might be false positives.
As such, I would like to know:
Was probablement je n'y mourrai pas formerly acceptable, at least in some registers? If so, when did this change, and was this true of any other adverbs?
Is probablement je n'y mourrai pas really so egregiously ungrammatical nowadays that one might "correct" by adding que? I imagine that this addition stems from translating from the English script rather than quoting from the original novel, but I also wonder if it is an attempt to update the grammar of the text.