Hi All,

I have an iMac Pro 2017 that I have converted to Linux. My goal is to turn it into a MythTV frontend for the kitchen area.

I tried several Ubuntu 20.04 based distributions (Xubuntu, Lubuntu, Kubuntu) before finally settling on KDE Neon User Edition 5.21. All the other distros worked fairly well, but KDE Neon seemed to work best of all, with one of the most important deciders being its ability to properly turn the screen off when the computer is idle, rather than just making the screen black (ish) but with the backlight still on. So thanks to all who've worked to make it work so well on the iMac Pro hardware.

FYI For anyone else who tries it, the kernel parameter: amdgpu.dpm=0 was important to make boot up and shutdown fast whilst retaining screen powersaving capabilities.

My (final?) issue is that I can't get the headphone jack, which I use to connect to external speakers, to put out any sound. The headphones are detected when I plug them in, the onboard sound stops, volume widget shows connection, high volume, and pulsating blue bar indicating sound playing, but no actual sound through the external speakers.

I did check the headphone jack and/or speakers aren't broken - and yes it works just fine when I boot into the standard Mac OS Big Sur.

I note that alsamixer shows the headphones muted. I unmute them and turn up the volume. But still no sound through the headphone jack. And then when I reboot, alsamixer has gone back to showing them muted. So maybe that's a clue to the problem? But even if so it doesn't get me closer to a solution yet.

Has anyone else experienced and hopefully overcome this problem on the iMac Pro? Or just have a clue to helping point me in the right direction?

Thanks in advance,
imaclover