Changing audio device

In Win10, with speakers and headphones turned
on, I can switch between these devices. In KDE, in order to have sound
from the speakers, they must disconnect the headphones. Is there any
solution to this?

Being able to select output port is a feature that most of the time depends on the Windows proprietary audio driver of the device.

For linux you can sometimes enable that by modifying alsa card profiles and possibly even allow them to work simultaneously. I made a guide for that which you can check here: GitHub - luisbocanegra/linux-guide-split-audio-ports: Split jack(headphones)/speakers outputs into individual sinks on Linux to allow simultaneous playback (listen to different audio streams on each port)