I don't remember since when exactly, but since approx. beginning of 2020 I don't experience this issue anymore, I can happily charge my sleeping XPS13 over my docking station. I'm still running the Ubuntu 18.04, which was shipped and I regularly update kernel and firmware (both XPS13 & TB docking station). Thank you for fixing it.
When my XPS 13 9380 is in normal sleep mode in Ubuntu and I want to charge it over the TB16 dock, the system is going into a weird state, where it somehow wakes up, but doesn't show anything on the screen. And this keeps active even after charging and plugging out.I have to hard reset it by pressing the power button for more than 5s. If I forget that, the battery will be just be drained as if the system would run normally. It only works when I open the XPS before connecting it to the TB16 dock, plug it, charge it, unplug it and put it into sleep mode again. However not, while it sleeps. I assume there is some weird thunderbolt stuff going on. Is this a known problem or is there even a workaround setting any thunderbolt options in the BIOS or in Linux? CheersPhil                    
XPS 13 9380 + TB16 dock + Ubuntu: Charging while in sleep mode leads to freeze