At least half were written in what I took to be an authentic voice but with such bad grammar and spelling as to render them barely readable. Some had clearly been mangled in a laundromat of Google translate from Hinglish via Mongolian and Swahili. They contained bizarre phrases and comical statements. Many more were obviously written by some kind of generator and fudged until they read well enough.
Since the student handbook states the threshold for academic "plagiarism" is above 20 percent perhaps unsurprisingly the Turnitin (an awful tool) score for almost every essays was just below 20 percent. An interesting clustering!
Students who cheat have a formidable array of tools now, not just GPT but automatic re-writers and scripts to test against Turnitin until it passes.
Add to this problem that my time for marking is not paid extra, is squeezed tighter every semester, and that students are given endless concessions to boost their "experience". The handbook also says that if they fail, no worries, they get to try again, and again, and again... and I am sure if I actually stuck to my guns and failed every single student I'd be fired.
As I wrote in the Times last year, I think the technological arms race against GPT (and the economic conditions that mean it's used) cannot be won with the time and resources available to ordinary human teachers.