After reading various Holographic Remoting docs, it seems a very straightforward process.
On PC: Unity 2020, MRTK 2.7.2, OpenXR Plugin 1.2.8, MRTK OpenXR Plugin 1.0.2.
On Hololens: Holographic Remoting Player v2.6.1.0. And I can open the Hololens portal page from the PC.
Other settings are shown in the attached picture.

Everything seems right. Hololens "Waiting for Connection on ...", then I click the play button. However, Unity keeps running the app in the Editor window, nothing else happens. Not even an error message is shown in the console. I also tried the whole setup in a 192.168 network. Magic does not happen. What am I doing wrong? Any hint is appreciated. Thanks.