Comment 2 for bug 1980663

xterm is a false positive component-mismatch (MIR), as tk8.6 "Recommends: xterm | x-terminal-emulator" and x-terminal-emulator is provided by "gnome-terminal" in Ubuntu "main" already.

https://git.launchpad.net/ubuntu/+source/tk8.6/tree/debian/control#n20

$ apt install x-terminal-emulator
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Package x-terminal-emulator is a virtual package provided by:
  xterm:i386 372-1ubuntu1
  xterm 372-1ubuntu1
  xiterm+thai 1.10-2build1
  xfce4-terminal 0.8.10-1
  tilix 1.9.4-2build1
  termit 3.1-1
  terminology 1.12.1-1
  terminator 2.1.1-1
  stterm 0.8.4-1
  sakura 3.8.4-1
  rxvt-unicode 9.30-2build1
  qterminal 0.17.0-0ubuntu1
  pterm 0.76-2
  mlterm-tiny 3.9.0-1build1
  mlterm 3.9.0-1build1
  mate-terminal 1.26.0-1ubuntu2
  lxterminal 0.4.0-2
  lilyterm 0.9.9.4+git20150208.f600c0-5build1
  konsole 4:21.12.3-0ubuntu1
  kitty 0.21.2-1build1
  eterm 0.9.6-6.1
  deepin-terminal 5.2.11-1build1
  cool-retro-term 1.2.0+ds-5
  gnome-terminal 3.44.0-1ubuntu1
You should explicitly select one to install.

E: Package 'x-terminal-emulator' has no installation candidate