I would like to play
omxplayer in a service like VNC or RDP, etc.
You can do this with the RealVNC server which is installed by default in Raspbian. You simply enable it from the Raspberry Pi Configuration app, and you should see the VNC icon appear in the top right to show it's running.
If you click on this icon, go to Options > Troubleshooting and enable "experimental direct capture mode", this will allow you to capture directly-rendered screen content, such as that displayed by omxplayer.