Sound is available from speakers only when headphones are unplugged

Question

I've just installed Kubuntu 20.04 and I'm trying to use my speakers, although the headphones jack is connected.

When I connect the headphones, I can see in pavucontrol-qt "analogue headphones" as the output device and when i change it to line-out, the sound dissapears.

But when I unplug my headphones, the output device changes automatically to line-out and sound gets out perfectly from the speakers.

I've tried:

• Enabling "simoultaneous output" in paprefs but it doesnt work.

• Changing the Mute in alsamixer

With this one, I saw that the headphones are mutted with line-out. When I unmute them, they sound, but still not the speakers.

I made the speakers sound disabling auto-Mute, but now I can't hear the headphones, although they are connected.

There is another problem: I cannot route applications between headphones and line-out, there are just two options: analog stereo internal audio and simultaneous output to analog stereo internal audio (with this one is the same problem: either speakers with disabling auto-mute, or headphones).

If it is needed:

and a bild of output devices:

In "audio interno estéreo analógico" ports are the headphones or line-out options.

Motherboard: GA970A-DS3P (Rev.2.x) Audio Realtek ALC887 codec NOTE: I'm using just Realtek audio, I don't use HDMI audio

Answer 1

Finally something worked: in alsamixer I enabled Loopback and disabled Auto-Mute.

I also manually configured them in alsamixer and pavucontrol:

Go to output devices in pavucontrol, set line-out as port and set the headphones volume to "0", then set headphones as port and set "front" on "0" (without muting: when I mute it, all the sound mutes)

Now the routing is working well but I need to search for how to route a single app because I cannot see the option in pavucontrol or system audio.