Pretty sure Windows Phone did this over a decade ago. I mean, say what you want about Windows Phones, but yeah, this was a thing.
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The first modern thing like this that I can recall is the 2011 Android-based Motorola Atrix phone[1] that presented a DeX-like desktop (well before DeX!).
It used an Ubuntu-based desktop. It was really, really good, but never got traction.