Comment 9 for bug 1691025

xpra in 18.04 depends on xserver-xorg-video-dummy and xserver-xorg-input-void.

$ apt search xserver-xorg-video-dummy
Sorting... Done
Full Text Search... Done
xserver-xorg-video-dummy/bionic 1:0.3.8-1build1 amd64
  X.Org X server -- dummy display driver

xserver-xorg-video-dummy-hwe-16.04/bionic 3:14.1 amd64
  Transitional package for xserver-xorg-video-dummy-hwe-16.04

xserver-xorg-video-dummy-hwe-18.04/bionic-updates 1:0.3.8-1build3~18.04.1 amd64
  X.Org X server -- dummy display driver

while

$ apt search xserver-xorg-input-void
Sorting... Done
Full Text Search... Done
xserver-xorg-input-void/bionic 1:1.4.1-1build3 amd64
  X.Org X server -- void input driver

xserver-xorg-input-void-hwe-16.04/bionic 3:14.1 amd64
  Transitional package for xserver-xorg-input-void-hwe-16.04

1. Where is xserver-xorg-input-void-hwe-18.04 ??
2. xpra dev said they removed input-void dependency 4 years ago https://xpra.org/trac/ticket/2190#comment:14 Why the Ubuntu package still depends on it?

I think adding xserver-xorg-input-void-hwe-18.04 or removing xserver-xorg-input-void dependency at all would fix the installation problem.