Disposition of xserver-xorg-hwe-18.04 in system upgraded to 20.04
Solution 1:
The packages.ubuntu.com says that this xserver-xorg-hwe-18.04
package is transitional on Ubuntu 20.04 LTS and that it has size of 9 Kb.
So it may be safely removed by
sudo apt-get purge --autoremove xserver-xorg-hwe-18.04
This package was needed on 18.04 LTS to get newer components of HWE stack.
About the xserver-xorg-hwe-20.04
package you are right - it does not exist.