Qt Remote Objects use a QIODevice as a transport. Still, regular TCP/IP connections are the most used communication link and use case referred in the docs and examples.
Qt Remote Objects can be used over other transport links which can support totally different use cases. For example, if Bluettoh LE can be used, users can easily implement a companion app which controlls an embesses device via Bluettoh LE
There is an example for the latter pending reviews: https://codereview.qt-project.org/c/qt/qtremoteobjects/+/265305