Nope ... that did not solve it ....

Please note when I say "it looks like this problem" I'm talking about the original problem that started this thread ("looping back to the login screen"), not your issue which, by your own description, is "a totally different problem".

It's confusing to try to discuss different problems on a single thread; it would be better to create different threads for different problems... they don't cost anything! :D

displaylink-debian
 

Give this a try:
https://github.com/AdnanHodzic/displaylink-debian

...note that I was unable to get this working with the nvidia proprietary drivers. I had to use the nouveau drivers

Solution on github worked for me...
 

The solution on https://github.com/AdnanHodzic/displaylink-debian worked for me with ubuntu 18.04 upgraded from 16.04. it finds the HDMI monitor attached to the USB as a generic monitor and not LG, but it displays good the images.
The mouse pointer also flickers sometimes but it's not annoying.

displaylink-debian
 

Same problem
I tried https://github.com/AdnanHodzic/displaylink-debian, but after rebooting the X crashed and comes back to login again. Then I need to login in 'Ubuntu with wayland' and uninstall display-link then reboot.
:confused:

Finanlly it worked for me
 

It only worked with nouveau drivers.

I have a Dell Inspiron I5 Gamer, com GeForce GTX 1050 Ti Mobile.
1 Extra Monitor via DL-3000
1 Extra Monitor via HDMI

I did this:

1. Power off/on Dl-3000
2. Uninstalled all nvidia drivers: sudo apt-get purge nvidia*
3. reboot
4. download and run https://github.com/AdnanHodzic/displaylink-debian
5. reboot

This is my configuration:
+ uname -r
4.15.0-36-generic

+ systemctl status dlm.service
● dlm.service - DisplayLink Manager Service
Loaded: loaded (/lib/systemd/system/dlm.service; enabled; vendor preset: enabled)
Active: active (running) since Sat 2018-10-20 21:48:45 -03; 2 days ago
Process: 1124 ExecStartPre=/bin/sh -c modprobe evdi || (dkms install evdi/4.4.24 && modprobe evdi) (code=exited, status=0/SUCCESS)
Main PID: 1132 (DisplayLinkMana)
Tasks: 34 (limit: 4915)
CGroup: /system.slice/dlm.service
└─1132 /opt/displaylink/DisplayLinkManager

out 20 21:48:45 ub-dell systemd[1]: Starting DisplayLink Manager Service...
out 20 21:48:45 ub-dell systemd[1]: Started DisplayLink Manager Service.

+ xrandr --listproviders
Providers: number : 3
Provider 0: id: 0xf1 cap: 0x9, Source Output, Sink Offload crtcs: 3 outputs: 2 associated providers: 2 name:modesetting
Provider 1: id: 0xcb cap: 0x2, Sink Output crtcs: 1 outputs: 1 associated providers: 1 name:modesetting
Provider 2: id: 0x44 cap: 0x6, Sink Output, Source Offload crtcs: 4 outputs: 1 associated providers: 1 name:modesetting

+ lsusb -d 17e9:
Bus 002 Device 003: ID 17e9:4318 DisplayLink

+ lspci -nnk | grep '\[03'
00:02.0 VGA compatible controller [0300]: Intel Corporation Device [8086:591b] (rev 04)
01:00.0 VGA compatible controller [0300]: NVIDIA Corporation GP107M [GeForce GTX 1050 Ti Mobile] [10de:1c8c] (rev a1)

Thank you madscientist. I had the same issue (I have ASUS MB169B+ as second monitor):
1. Mouse cursor artifacts on GTK menu bars.
2. After rebooting laptop with connected usb cable the monitor is not connected.
But now both problem are solved.

Workaround (works on ubuntu 16.04)
 

I'm still in Ubuntu 16.04, and have the same issue on mine Lenovo Ideapad 720S with Nvidia 1050 on board.

I found the workaround is to log-out and log-in again once OS is started.

BTW. tried 3 lates versions of driver and the issue persists.

I published this video with the issue: Display Link issue with cursor

Solved it by restarting display manager
 

Hi everybody, had this issue for some time on different Ubuntu based distros.
Nvidia + DisplayLink and one external display.

Mouse flickering was present on builtin display.

I've managed to solve the issue by restarting display manager service.

Hope this helps.