I am the owner of a DELL WD15 Dock and a Dell U3818DW monitor. I bought the dock to quickly switch between both of my macbooks.... But seems happen to not work as I'd like to.
On my Macbook Pro 2017 13", on Mojave 10.14.6, on the display options, if I press "option + scaled" to get the full list of available resolutions, I can get 3840 x 1600. On that one, the dock works like a charm.
On my Macbook Pro 2018 15", on Catalina 10.15.5, the maximum resolution I can get is : 1920 x 1080. But it works if I use the HDMI apple adapter (but it is not handy to unplug the monitor from the dock every time).
Has anyone ever faced that situation? Please tell me you found a solution! 🙏 Thank you anyway, and have a great day,
PS : the monitor is connected with HDMI.