Apparently, this has nothing to do with the Dell Dock.
I have removed all peripherals, rebooted. And the problem is solved!
– mr LJun 02 '20 at 10:29
Could you please expand your comment to an answer (e.g. how to remove all peripherals, which command(s), if any, to run etc.) and post to [this question](https://askubuntu.com/questions/1239006/what-does-the-indicator-icon-with-three-dots-over-a-power-plug-mean-in-ubuntu-20) to help future readers. Thanks.
– pomskyJun 02 '20 at 10:34