@gabek I have a Lenovo t480s which came with a Lenovo Thunderbolt 3 Dock Gen 2 and I run Ubuntu and Windows on it, both work fine with the dock. (actually I should specify, everything except the audio works perfectly, the headphone jack on the dock still has obvious software glitches that happen randomly after 5min to an hour of use..)

I heard that there was a terrible bug in the Lenovo thunderbolt driver/firmware which would actually eventually destroy the thunderbolt controller in the laptop. It sounded like the longer the laptop ran with that bad firmware/driver, the more likely it would be damaged.

I tried as much as I could to update the thunderbolt driver/firmware. Some of this might only be possible from windows. I'm not sure. IIRC there was also an official Thunderbolt related package that Lenovo released for Ubuntu.