WindirStat was based on KDirStat[0] (which apparently has been superseded by qdirstat[1], this is the first I've heard of it) for KDE. Baobab[2] is a similar tool for Gnome.
A bit slower, but I just use totalcmd to display sizes of all direct subfolders. Check both program files' folders and then user folder (and work my way into appdata).
To easily answer this question I always use a tool like
https://windirstat.info/ (Windows) or Baobab (Linux)