Comment 27 for bug 1834771

I'm also affected by this bug under Linux Mint 19.2 and with Radeon RX 580 (amdgpu driver).
With all new Kernels from 5.0.0-16 on my HDMI monitor isn't recognized as "plugged in" and I don't have audio output. Pavucontrol shows all available HDMI imputs as "unplugged".

Going back to 5.0.0-15 Kernel fixes the issue for me but this cannot be a long term solution. Over the last months I searched a lot in different Ubuntu/Linux Mint forums and found many people having this exact issue. All of them with amd graphics.

Finally found the root of this problem: This faulty behavior seems to be introduced with this bugfix:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1827967

All Kernels from 5.0.0-16, 4.15.0-51 and 4.18.0-21 on are affected. In forums I found examples of all three Kernels.

reply #26:

As I (and probably also Gary Altenberg - #24) don't have any Nvidia chips along our amd graphics, I have no idea how the nvidia proprietary driver could help. ;-)

If I understand the bug description of https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1827967 correctly, the problem was that there were some unnecessary sound devices that could confuse users. In fact, the patch might have broken hdmi sound output for most amd graphics users by removing all of the entries.

Please fix that issue or if not possible revert the change! Having some unnecessary entries to chose from is better than having no sound at all. :-)

Here are two examples of affected user from forums (but you can find many more):
- https://forums.linuxmint.com/viewtopic.php?t=295685
- https://askubuntu.com/questions/1032811/ubuntu-18-04-no-hdmi-audio-with-amd-radeon-hd-7870/1150624#1150624
- ...