It is known bug 1245473.
Nobody cares about it even on modern Ubuntu Community.
I'm citing my other answer here:
Myself I found only one resolution - I'll stay on Ubuntu 16.04 LTS MATE until 2021 year (really 2019 because it's Ubuntu flavor).
In Ubuntu 16.04 LTS MATE I use Ctrl+Shift without issues.
I have created PPA with patched packages for:
- Ubuntu 16.04 LTS (xenial) with xserver-xorg-hwe-16.04
- Ubuntu 18.04 LTS (bionic)
- Ubuntu 18.04 LTS (bionic) with xserver-xorg-hwe-18.04
- Ubuntu 18.10 (cosmic)
- Ubuntu 19.04 (disco)
- Ubuntu 19.10 (eoan)
- Ubuntu 20.04 LTS (focal)
- Ubuntu 20.10 (groovy)
- Ubuntu 21.04 (hirsute)
- Ubuntu 21.10 (impish)
You can test them by the following commands:
sudo add-apt-repository ppa:nrbrtx/xorg-hotkeys
sudo apt-get update
sudo apt-get dist-upgrade
Warranty disclaimer: packages were tested in
- 16.04 LTS with HWE (Unity, MATE, Xfce)
- 18.04 LTS (Cinnamon, KDE, MATE, Xfce)
- 18.10 (Cinnamon, KDE, MATE, Xfce)
- 19.04 (Cinnamon, KDE, MATE, Unity, Xfce)
- 19.10 (Cinnamon, KDE, MATE, Unity, Xfce)
- 20.04 LTS (Cinnamon, KDE, MATE, Unity, Xfce)
- 20.10 (Cinnamon, KDE, MATE, Unity, Xfce)
- 21.04 (Cinnamon, KDE, MATE, Xfce)
- 21.10 (Cinnamon, KDE, MATE, Xfce)
However other desktops may have issues even after applying the patch.
These packages do not fix problems for GNOME Shell (18.04 LTS, 18.10, 19.04, 19.10, 20.04 LTS, 20.10 and 21.04) and Unity (in 18.04 LTS and 18.10). To remove GNOME Shell and install other desktop follow my other answers - for 18.04 LTS and for 20.04 LTS.