Redirected here after Leigh noted it wasn't a direct Cinnamon issue in my Bugzilla report (https://bugzilla.redhat.com/show_bug.cgi?id=1808934).

For EL7 users, using a minimal installation, adding EPEL, then performing yum groups install "Cinnamon Desktop" does not result in a usable system as the X11 server is left out of the dependency chain, unlike on Fedora.

I'm honestly not really sure where to put this report as xorg-x11-server-Xorg is a part of the "X Window System" (or x11) yum group, but xorg-x11-drv-libinput was needed (which will pull in Xorg) in order to have lightdm accept user input to login. That package is also in the x11 group, but as an optional package. Without the XOrg server, lightdm fails to start, so I'm not sure if I should be reporting this here or as a lightdm bug.