Checked the minimal version of DE XFCE - gives an error. This means that among the packages that are included in the lists of additional groups, there is something that allows quemu to work correctly. Now I will look for this "something".
Thank you for documenting the steps you made and thank you for actually reading the documentation (first). Most of the people try first, then complain on forums and only then they check documentation
It will help us to improve the system and also to check if upcoming structural changes / improvements, which are planned to be merged within 4-6 weeks, will not break what you just achieved / the user customisations. Changes are mostly related to desktops, but some basic principles are also changing / improving on the way.