Same problem here, with a DisplayLink dock station and a Thinkpad P1 (1st gen) with the NVIDIA (Quadro P2000) card disabled, running only on the iGPU that comes with my Xeon E-2176M CPU.
It's so unusable that I basically had to move back to using an NVIDIA-only mode and plug the screen directly over the laptop's HDMI port, which makes now the dock station a "glorified pots hub" :-).
This said, I believe this is in general a known issue of the DisplayLink drivers for Linux, and not necessarily related to Ubuntu or the Linux kernel. Reporting anyway in case I'm wrong and there's a chance to make this work properly, which would be awesome for many reasons (e.g. I could go back to the iGPU-only mode).
Same problem here, with a DisplayLink dock station and a Thinkpad P1 (1st gen) with the NVIDIA (Quadro P2000) card disabled, running only on the iGPU that comes with my Xeon E-2176M CPU.
It's so unusable that I basically had to move back to using an NVIDIA-only mode and plug the screen directly over the laptop's HDMI port, which makes now the dock station a "glorified pots hub" :-).
This said, I believe this is in general a known issue of the DisplayLink drivers for Linux, and not necessarily related to Ubuntu or the Linux kernel. Reporting anyway in case I'm wrong and there's a chance to make this work properly, which would be awesome for many reasons (e.g. I could go back to the iGPU-only mode).
Hope this helps, and thanks!