@Luksus Luksus, I'm sorry, Headphone output working as it should. Maybe a reboot did the trick ... . Thanks and sorry for the confusing message ... Ciao and thanks!

@Luksus After an OS update the same problem returned. I tried to do the same trick again, but to no avail. When I try to reload pulseaudio I got:
root@ubuntu-phablet:/home/phablet# systemctl --user restart pulseaudio.service
Failed to connect to bus: No such file or directory

@MrT10001 Ok, it worked as you said without bothering about the developer mode, thx for your help!

@MrT10001 How do I enable developer mode if I cannot acces the device?

Yesterday I pushed ok to install the update that was advertised in my OnePlus6 with UT Focal Fossa. Now it doesn't boot up anymore.
Looking in the logs in recovery mode I read something like 'not enough space on the device'.
Is my phone corrupted by an incomplete update?
Do I have to reflash an reinstall everything?
If there is any other way I'd be grateful to be informed about it.
Greetings
Tom

@Luksus This worked for my wired headphone issue on my OP6. Thanks!

@ancientsounds I've had my problem solved following the instructions in this post

@ancientsounds
I have a mini jack audio output (female). Never had audio over USB-C ...

@DPITTI
The plug on my cable works: I have a second oneplus 6 with linageOS installed and also my laptop: they both play nice. My headphones' jack is fine too ...

What is hard to check is the plug in my phone: I never tried it neither on Ubuntu nor on android. Should I reinstall android to check? I would like to avoid that, having finetuned and installed everything last week, planning to make it my daily driver ... .

I tried uVolMan fork (the only vol manager available in my open store). Nothing seems muted.

Now I noticed some strange behaviour:
The music player plays back on the speakers, but the moment I plug in the headphone jack, the playback stops (no seconds add up any further). When I unplug, it continues playback over the speakers from the point it stopped when I plugged in the headphone jack ... .

Curious if anyone can explain what happens here.

Hello,
UT 20.04 on Oneplus6 untill now working nice, waydroid with microg too.
Today I have noticed there is no audio coming out of the headphone out minijack plug that I normally connect to my stereo.
Bluetooth works. But that is to a bluetooth speaker while on holidays. No sound to my (wired) HiFi system.
I thought to let you guys know ...
Greetings
Tom