FWIW - on Ubuntu 18.04 I started using UKUU to get the latest 5.1 stable kernels, and the whole experience has just been far better than the stock 4.15 kernel, HWE 4.18 kernel and HWE-Edge 5.0 kernels provided in the main Ubuntu repos.
I have a Dell D6000 dock and a Dell XPS 9370 and I'm still able to use the dock without issue, plugged into a single 4k monitor via the HDMI interface. The DisplayLink drivers never worked with the 2 DVI ports, and I haven't tested those with the 5.1 kernel yet, so all I can claim is at least feature parity.
I have successfully uninstalled the DisplayLink and EVDI drivers without losing any functionality. In fact, I no longer have the DisplayLink process hogging between 20-50% CPU constantly, so a big win there.
I did have a quick skim of the
LWN kernel archives to see if there was any obvious support gained by the kernel but didn't find anything relevant, so I'm at a loss for why this even works.
Other than that, battery life on the laptop has improved even when disconnected from the dock (even when I hadn't yet removed the DisplayLink drivers and service). And both bluetooth and wifi are slightly more reliably when it comes to suspend/resume.
I'd be interested to know if others are able to forego the DisplayLink driver with other hardware and an upgrade to the 5.1 stable kernels.