I'm using a Logitech K120 keyboard (105 keys) on Ubuntu 20.04 and in all other applications I can use the quotes (double and single), but in PhpStorm I can't. It happens to me with quotes and other characters like '~'.
What should I do? I have already used dpkg-reconfigure locales and it still doesn't work.
I had the same problem and found the solution in this issue: https://youtrack.jetbrains.com/issue/IDEA-78860
You must change the IBUS setting on the keyboard. I did it in the same graphical mode without using any commands (I'm not very good at that yet).
PS: You must restart the PC or at least log out.
I hope it works for you.