file_path = await new_dialog.files_selected

You probably want file_selected, not files. When the file mode is set to single file, then only file_selected signal is emitted, and when the file mode is set to multiple files, only files_selected is emitted. So if you use await files_selected when file mode is set to single file, then it will be stuck forever.

I just tried to update and it failed with error 403 when it tried to download the kernel, so it seems like they took measures.

You can skip it with the --skip-launcher launch option