- What are some differences with connecting a monitor to the HDMI port vs. the USB-C port?
- Can you close the lid of the laptop and continue working on the monitor(s), even with a bluetooth keyboard/mouse?
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See here, well explained: https://www.howtogeek.com/661325/should-you-use-hdmi-displayport-usb-c-or-thunderbolt-for-a-4k-moni/
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Yes, should be possible.
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Your link is quite informative. It does raise questions about the supported standards of the L14 though.
What HDMI and DisplayPort version will be supported? And in case of the latter - does using DisplayPort over USB-C have any effect on throughput / does it support the mentioned display stream compression?
Thanks in advance for helping me choose a new monitor 
If confirmed that would totally do, thanks. For anyone else about to choose a new monitor - that is a page to calculate if a device matches the laptops capabilities: https://linustechtips.com/topic/729232-guide-to-display-cables-adapters-v2/?section=calc&H=3440&V=1440&F=100
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Mladen’s information is correct, as usual
For using type-C to attach to a screen you of course then also need a type-C to $something adapter, unless your screen can cirectly be attached to a type-C source. Adapters come in large varieties, you can get type-C to DP adapters or type-C to HDMI and with or without additional USB hub function. Depends on your use case.
Cheers
nicole
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Well it does affect the throughput of the USB connection! Hence the decision in part depends on what else you might want to do with the USB-C port.
The decision also depends on the capabilities of the monitor.
In the absence of other information, I would stick with HDMI for the external monitor (and charging via the regular DC-in connector). Then the USB-C port is completely free to use as a USB port.
At the other end of the spectrum, some people like to use a dock, connected to a laptop via USB-C, that has everything on it (power in to the laptop, video out to the dock which then outputs either HDMI or DP to a monitor, ethernet, and a couple of USB ports typically for keyboard and mouse).
That is what I’m planning to do. Get rid of the cable tangle on my desk and reduce it to one. Right now, I don’t really see any advantage in using the HDMI connection - DisplayPort 1.2 supports up to 17.28 Gbit/s of which I need 12.76 Gbit/s for the screen. The rest seems plenty for internet, mouse and keyboard.
Also thank you @nicole.faerber for your confirmation. I chose a monitor with USB-C including DP, USB hub function and power delivery (assuming that 90W will do).
Right, the problem is that there are only that many lanes on the type-C plug. The higher data rate you want to have the more lanes you need. For USB3 SuperSpeed modes you need two more than for USB2. For DP 4k @ 60Hz you need two more than @30Hz. So in effect this means either high speed USB or 60Hz with 4k. So you can not have both from the same plug, I’m afraid.
Cheers
nicole
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What Nicole said. 
Where it can make a difference is if you are e.g. backing up to an external USB drive. A decent one that is capable of higher speeds. However fortunately the Librem 14 has two USB-C ports anyway (as well as a couple of good USB-A ports).
Also, there is a difference between “ethernet” and “internet”. However if you are really only using the internet then most likely there is enough for the internet. But in that case the WiFi by itself is usually adequate and you don’t strictly need ethernet on the dock.
Follow up on this topic @nicole.faerber, if I may. When I connect my usb-c monitor to the L14, it only seems to detect the usb-hub (and attached devices) but isn’t outputting display. Any advice on where to start troubleshooting?
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Did you connect to the correct one of the two USB-C ports? I believe that only one of them does video (whereas obviously both of them do vanilla USB device connection aka data).
Haha yes, I got that far at least. It looks like the USB hub in the monitor is being recognized but the display is possibly only registering add a billboard device. Not very familiar with this area but I’m trying to chase it down.
Promising to at least likely know that the negotiation is failing but could definitely use some help trying to identify a solution or cause.
Anything in the system log?
It may help to identify exactly what monitor you are using, what its specifications are, what connection type you are using (in full) between the USB-C port on the Librem 14 and the monitor.
My knowledge is insufficient to decipher the lsusb -v output to know really what it is trying to tell you.
Do you have any alternative monitors that you can try? (including some that might need a USB-C to HDMI or DisplayPort adapter)