XPS 13-9380, 18.04 LTS, DA300 dock, HDMI not working

Also i suppose that da300 is not a thunderbolt adapter so it shouldn t work in 4k60hz, but my screen colors are corrupted in any other resolution (not a screen problem) conected to any port on tv or laptop. Ubuntu doesn t recognise DP to HDMI cable (dp connected to da300), ubuntu recognise vga to hdmi cable (with external ac), but tv doesn t recognise that signal at all. Ethernet usb a and usb c work normal on da300. Tried all settings for thunderbolt in bios. I also suppose that edid data from my tv is wrong, but it doesn t explain why dp port doesn t work on da300.

@polipropillon  I can't address the color issues, but I can answer the questions about refresh rate (in more detail, because Thunderbolt isn't the only factor) and also why the DP to HDMI cable isn't working with the DA300.

First, refresh rate.  The DA300 does support 4K 60 Hz, but only when connected to a system that supports DisplayPort 1.3 or better via USB-C.  The XPS 13 9380 and almost every other laptop out today only supports DisplayPort 1.2 because current Intel GPUs don't support anything newer, and even systems that have discrete GPUs typically still have most or all of their display outputs wired to the Intel GPU for final output.  This limitation will start to disappear starting with Intel's "Ice Lake" CPUs that will include a new Gen 11 GPU that will support DisplayPort 1.4 over USB-C, which are expected to arrive at the end of this year starting with CPU models meant for systems like the XPS 13, but obviously that doesn't help the existing 9380.

As for the DP to HDMI cable, those only work when the source DisplayPort output supports "Dual Mode DisplayPort", also known as DP++.  That technology allows a DisplayPort output to send an HDMI signal instead of a native DisplayPort signal.  The vast majority of DisplayPort outputs built into actual PCs and GPUs support this, and the DisplayPort outputs found on docking stations and DisplayPort MST hubs sometimes support this, but the DA300's DisplayPort output does not.  It only supports sending a native DisplayPort signal.  There are some active DisplayPort to HDMI cables and adapters that actually have a converter chip built into the cable/adapter itself, which WOULD work because in that case the DA300 itself is still sending a native DisplayPort signal, but most DP to HDMI cables are passive because they're designed to be used with DP++ outputs.  HDMI to VGA cables/adapters will work because those are all active since HDMI outputs have never supported sending a native VGA signal, and for that matter DisplayPort to VGA cables/adapters are all also active for the same reason.

Ok, now i understand something. So da300 isn t thunderbolt dock, right? It should work in 4k30hz through display port. Than i suppose it is ubuntu problem because it doesn t recognise any hdmi output. Xrandr says that there is edp-1 (notebook screen), DP-1 and DP-2, no hdmi. When i connect hdmi-hdmi cable DP-1 starts working. I suppose that it tries to send display port signal through hdmi, so that is why i have broken colors. Also system logs say something like [drm:drm_add_edid_modes.part.33 [drm]] *ERROR* Unknown HDMI VIC: 0. Idon t know what does it mean, and i didn t found it by google. Seems like some kind of kernel problem (not only on ubuntu. i ve tested different kernels and systems)

ps so i think i should buy Dell WD19TB that is much more expensive. Ubuntu site says that it is tested with 18.04 lts. Can you confirm that it works correct?

Ok, from now i bought tb16 dock and it works perfect. Seems like linux doesn t support usb-c to hdmi docks. Tried on different sets in shop and it didn t work with da300 and any other usb-c to hdmi adapter.
PS da300 works good on windows

Finaly i can say that xps9380 doesn t work with any kind of type-c to hdmi adapter using display port on any linux kernel. Only thunderbolt.