DisplayPort over usb-c for Librem 5?

Hi guys,

Will Librem 5 support DisplayPort over usb-c in order to connect the phone to a monitor/dock station ?


Yes, this is planned.

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Works fine for direct cable connection.

Does not work for me via USB-C dock.

I purchased about 8 different “USB-C Hub” with DP (no cheap crap)
to try and get Librem5 connected.
Fine & flawless: Charging, Trackball, Keyboard, Ethernet. They always work with Librem5.

Display dark. Monitor-Display worked in 0 cases.
Not even a flicker.

  • via DP Displayport from Librem5-USB-C to dock to monitor: dark
  • via HDMI from Librem5-USB-C to dock to monitor: dark

Any combination dark.

Even worse:
The Librem5 recognizes the display size of the dark but connected monitor and switches to multi-monitor mode!
So mousepointer and windows disappear on a not operational Monitor-Display.

With several different Laptop brands ALL of these combinations worked fine.
The Librem5-USB-C to (NEC-)Monitor-Displayport direct connection works fine. So Librem5 and (NEC-)Monitor understand each other well.
The Monitor understands all frequencies “spoken”.

PureOS 10 (Byzantium) Linux pureos 6.5.0-1-librem5 #1 SMP PREEMPT Fri Dec 8 19:43:40 UTC 2023 aarch64 GNU/Linux

Of course Librem5-Display itself is not disappointing.
It’s working fine all the time.
Not providing proper video signals to Monitor Display is disappointing.
Since ALL Laptops-to-docks-to monitor combinations via USB-C work fine
ONLY the Librem5 fails
I am disappointed and have a question:

What do I need to do
to get Librem5-to-dock-to monitor

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I vaguely remember someone posting a few years ago a list of usb hubs that worked and those that didn’t. I don’t have a link for you, just hoping that gives you a tip on what to search for.

I also do know that the quality of hdmi / usb-c and other cables is REALLY REALLY REALLY bad in general. Here is a Linux Tech tips testing cables where 50% had failure rates: https://www.youtube.com/watch?v=XFbJD6RE4EY&t=5s

Also, don’t forget that hdmi / usb cables come rated at 100 000+ plug/unplug capacities. Just because they are rated as such, that doesn’t mean that flaws and day to day use doesn’t introduce issues ESPECIALLY when you introduce intermediary devices such as hubs.

Just some details to consider, you probably already know though.

For me, if I go into the settings and reduce the resolution on my connected monitor, it usually works. But I also tend to switch to 1 output, displaying only on the DisplayPort through the dock, at which point the phone goes dark and the monitor which is in the bug state you described then lights up and works.

So, either my DisplayPort dock is better supported by the L5 or else more likely it has trouble with some DP configurations but not all.

As mentioned earlier there is a list of compatible accessories. It is located in the community wiki.


There’s also a table here, which isn’t always kept in sync with the one in the community wiki:


Thanks a lot for your effort and kind care.
well, no.
No, that’s not the issue. I can prove now.

All you need is a miracle.

Changing resolution and other settings was in vain, as expected.
All the time there was 30,0 Hz on offer (the dock can not do better and thats fine regarding 4K-UHD).
After some weeks fiddling with the same equipment I suddenly was offered the frequency to choose two times. So there suddenly was 30,0 and 30,0 Hz. Exactly the same, right.
I bravely chose the other one.
And it works.
So all the equipment was capable all the time.
You can not blame the NEC monitor: Too expensive to fail.
Neither the Librem5 (for the same reason).
Probably there was a slight misunderstanding on the frequencies second decimal place. I will follow up what experience is more common. The dark or the coloured monitor.
Reminds me: In the eighties my Hyundai monitor experienced sync issues, too. I had to overheat it before use.
Librem5 rather swallows miracles … :slight_smile:

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