Darktable is installed on two computers at my place. The problem is only on one of the computers. Both are running the same OS (Manjaro).
When I hover the mouse over the “full path” in ”image information” or the symbol in the top right corner (history) of Lighttable, I get no text on one computer. It seems that the help texts are missing.
This happen in more spots. I have “Show tooltip” checked.
Did you, inadvertently, turn off the tooltips on that machine?
shift+t to turn on/off.
EDIT:
Even if you have the show tooltip (un-)checked in the thumbnails overlay section you can turn the tooltips on/off using the shift-t option without influencing that setting.
Not sure if that is by design. I would expect the setting to change if your use shift-t to turn it on/off. Maybe the devs see using shift-t as a quick and temporary thing.