Often, the graphical interface (i.e. Software app) to the PureOS repository malfunctions.
You can remove WAAAA using the terminal instead. I first looked for the actual package name with apt search WAAAA
(I don’t have it installed) and discovered that it’s name in the repo is waaaa
. (Case matters in Linux terminal commands.)
So sudo apt remove waaaa
should do it.
If it were a flatpak instead of a native PureOS package, the command would be flatpak uninstall waaaa
. (But it’s not a flatpak.)
The author of that game is @dos, by the way.