Some recurrent problems, which I'm tired of having to solve over and over.
In some installations, Ctrl+^ does not produce the superscript, Ctrl+/ does not produce the fraction, etc. Keyboard shortcuts are defined in the file named KeyEventTranslations.tr. This should be located in the directory specified by:
FileNameJoin[{$InstallationDirectory, "SystemFiles", "FrontEnd", "TextResources",
$OperatingSystem}]
The returned directory did not exist. So I linked it to one that did:
/usr/local/Wolfram/Mathematica/14.0/SystemFiles/FrontEnd/TextResources$ sudo ln -s French/ Unix
and that fixed the problem.