So I installed the dnf group “deepin-desktop” and to my surprise, it force installed Chromium on my machine, why is that? does deepin-desktop have a dependency for Chromium or is this just a “preferred” package that the person whom created the group felt that it was nice to have?
It is a group dependency, see:
dnf group info deepin-desktop
You should be able to install these packages selectively.
As you can see here: https://pagure.io/fedora-comps/blob/master/f/comps-f30.xml.in#_823, the deepin desktop maintainers took this decision to include chromium as a default application (In any group, there are four levels of packages: optional, default, mandatory, and conditional […] Default can be unchecked).
If you wish, you can get in touch with them in order to discuss the decision: https://fedoraproject.org/wiki/SIGs/DeepinDE