At my University (UK), while any final decision on plagiarism/academic dishonesty is made on a case-by-case basis after looking through all the facts and evidence, what you describe is usually the best form of evidence the students can provide.
(Typical cases in which this might help so far were when a student would work on a lab machine and leave their solutions open without logging out properly. Then, somebody else would come along and opportunistically copy their solution. Usually, this is about programming assignments, but it does not have to be).
A history of older file versions, with the timestamps, showing how your work was created, and especially if it doesn't otherwise contradict your narrative, would most likely be more than sufficient to disprove any academic offences allegations.
While I acknowledge the issue mentioned by Vladhagen, that ChatGPT could just as easily produce an early, 'draft' version, and several refined version, as it could the final submission, I would argue that this is more effort than most students attempting to use ChatGPT typically spend on their assessments. If all the five versions were updated at the same time (or with e.g. 30 mins between them), it would actually point to foul play: normally revising self-written text takes some time. So, to make it look realistic but still use ChatGPT, the person attempting to cheat would need to have substantial delays (1-2 days) between their repeated uploads.
While it's not perfect, and could be manipulated in many ways, again, I doubt many students who decided to use ChatGPT to cheat would actually put that much effort into the assignment (because, at that point, you might as well try to do the assignment instead). It probably won't be a trustworthy piece of evidence in e.g. a court of law, but it will likely go a long way to disprove allegations of academic dishonesty in the academic circles (in fact, academics seem to be considering it to disprove allegations of using ChatGPT in their 'essays', i.e. papers).