There’s a package on pub.dev 407 for pytorch mobile, however it only works for android and it hasn’t been updated since its release in October.
I’ve been meaning to work on a plugin as well, but I’ve been swamped with other stuff   If I ever find the time to work on it I’ll be sure to update this thread.
And note that there’s no PyTorch runtime for the browser, so Flutter web is out of reach (until someone comes through with a version of torch.js).