My docking station with external monitor stopped working one day. I went to the cli and did ‘sudo dmesg -w’. I was getting lots of lines to do with the power supply. Turns out I wasn’t using a pd power supply and whatever supply I was using didn’t have the required power to run the docking station. Went back to the charger that came with the phone and it all started working again.
Or, precursor question, does HDMI even show up as an available audio sink?
Is this the one that Purism sells? (If so, dare I ask whether you are plugging it in correctly i.e. tail of the hub goes into the Librem 5 and the other USB-C port, at right angles to the tail, is used for power input to the hub?)
Random comment: Another option for debugging video output is to get a USB-C to HDMI adapter.
To be honest, I just went out and bought such an adapter, without any information on this forum or the Wiki as to whether it would be compatible with the Librem 5 - in fact purchased before I even had delivery of my Librem 5. I have tried that adapter on my Librem 5 with two different monitors and it worked with both.
I understand that that is not at all useful if you need the full functionality of a dock - but it can fault isolate.
(I actually don’t need the full functionality of a dock because I am using a Bluetooth keyboard with built-in trackpad. It all depends on your personal requirements, available hardware and setup.)
Sound over HDMI is already working with the latest kernel, but a) you need to switch to and out of it manually b) the audio device is not clearly labeled in settings. Both of those things will be fixed by librem5-base update that’s about to migrate over the next week. You will still have to switch the audio device manually the first time, since there’s no way to detect whether the connected screen actually has any means to output the audio (some screens only have a headphone jack, for example), but once you do that it will properly switch on hot plug and unplug.