I used windows-list with all my versions of Ubuntu, usually just manually installing the package. Lately I had to switch to python3 (don't ask) and I can no longer install window-list (Ubuntu 20.04).
window-list : Depends: python-appindicator but it is not installable
Depends: python:any (>= 2.6~)
Depends: python-wnck but it is not installable
I tried to install with window-list_0.10_xenial_all.deb