I was just provided with a new Dell XPS13 7390 laptop for work running 18.04.3 LTS. I need to get a dock for my peripherals and, since this thing has Thunderbolt ports, I'm considering getting a Thunderbolt dock that can (allegedly) run two external monitors at 4k, but don't want to spend the extra money if it won't work. I really have two basic questions:

Can I run two external monitors at 4k over Thunderbolt with Ubuntu 18.04.3?

Bonus: Can I run two external monitors at 4k and use the laptop display as well?

We purchased the Dell WD19TB dock and, after some good times, got it working correctly with the Ubuntu 18.04 laptop. Today, I attempted to hook up two external monitors and cannot get it working. I've tried the following combinations:

Scenario 1
Monitor 1: DisplayPort via dock
Monitor 2: HDMI via dock
Result: Only the DisplayPort monitor works, neither the HDMI nor the native display work. When I unplug the HDMI monitor from the dock, the native display does not return to function.

Scenario 2
Monitor 1: DisplayPort via dock
Monitor 2: DisplayPort via dock (the dock has two standard DPs and one mini DP)
Result: Only Monitor 2 works. This one is really curious, as xrandr shows all three connections, if I'm reading it correctly. However, --listmonitors only shows 2 monitors. I can provide xrandr results if requested.

Scenario 3
Monitor 1: DisplayPort via dock
Monitor 2: USB-C to HDMI via an adapter from the laptop's built-in USB 3.1 Gen 2 Type-C port
Result: None of the monitors work.

I can't even find a basic tutorial on how to get two external 4k monitors to work on Ubuntu, let alone with any of the configurations I'm dealing with. Does anyone have any guidance?

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    Ports and Slots Ports & Slots at dell.com/en-us/shop/cty/pdp/spd/… says ... 1. Thunderbolt™ 3 with power delivery and DisplayPort (4 lanes of PCI Express Gen 3) | 2. 3.5mm headphone/microphone combo jack| 3. Thunderbolt™ 3 with power delivery and DisplayPort (4 lanes of PCI Express Gen 3) | 4. microSD card reader so it may be possible. To be sure, ask Dell; if it won't do it with Windows, it surely won't with Ubuntu. – K7AAY Nov 11 '19 at 22:34
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    @K7AAY - I'm almost certain that it will on Windows as I could run two 4k's from different ports on my old laptop. I was just wondering if 18.04 supported it at all, or is that something that could possibly be supported given the correct drivers/packages? – AJ. Nov 11 '19 at 22:37
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    Short answer: yes. Long answer: YES and YES. First you have to buy the right Thunderbolt 3 device that supports Linux. Beware of the ones that only support 4K at 30Hz refresh rate. They are harder on your eyes. – WinEunuuchs2Unix Nov 11 '19 at 22:58
  • @WinEunuuchs2Unix - This is exactly the kind of information I'm looking for. Would you be willing to add an answer with this information and, if you're willing, an example of a Thunderbolt 3 dock that supports Linux? – AJ. Nov 11 '19 at 23:05
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    @AJ. I've only heard horror stories about docks not the good stories. My laptop has internal 1920x1080, TB3 to HDMI converter 4K@54 HZ, nVidia GTX 970M HDMI at 1920x1080. Three monitors work great. – WinEunuuchs2Unix Nov 11 '19 at 23:46

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