I bought an old Thinkpad T480 laptop to use as a separated laptop to work and travel. Everything was working fine, except that I couldn’t type / and ? in the keyboard.

After some search I found the solution:

1. Go to settings:
2. Go to keyboard and then “Input Sources” section.
3. Add a new source searching by ThinkPad (which results like “Portuguese”)
4. Make this source primary by moving it to up (or removing other sources).

Source: https://askubuntu.com/questions/184465/slash-in-thinkpad-t420-abnt-keyboard