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I have a Dell Precision M6800 laptop - about a 2015 model. I purchased a real docking station on Ebay for it for like $40 - one where the laptop sits in a cradle and a proprietary connection connects the 2. The dock station has 2 external display ports - I never could get my UHD monitor to work with them - so I use the display port of the laptop. Also for the last couple of weeks my display setting to only use the UHD would not work after reboot or logout - but if I momentarily reconnected the video cable it would work (or if go back into display setting and change it - that would also work). Installed plasma-wayland-session - and started logging in via wayland - both of those issues have went way. I figured I would post that datum point in case it was useful....
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