I decided to give it a try again on my Fedora 22 laptop, since I am happily using KDE/Plasma on my openSUSE desktop and in my personal opinion even though Gnome is now a great new and fresh desktop, I truly believe that it is far too heavy for its minimalistic look and approach and is missing some simple and quite common desktop features, for instance standard window buttons like minimize, maximized, etc. Also there are couple of nice features which you need to add as extensions and https://extensions.gnome.org/ is still showing "Beta" on the home page, for ages now. The desktop modification options are at their minimum. Simply it takes to much effort in my opinion to make default Gnome on Fedora to make it work and look the way you may want, at least for me. This is not good for a modern desktop these days, I believe. It gives me the feeling that Fedora (with Gnome) although open source seem to be very much like vendor locked, at least out of the box, do not get me wrong. KDE/Plasma on the other side, although also quite fresh and killed systray we knew for so long, still is much more flexible out of the box, I think.
My Fedora 22 is a long running laptop after several upgrades, changes, etc. I actually do not remember when I reinstalled it fresh last time. I have to say, fedup was doing a great job every time.
The way I did it.
First, I installed KDE Plasma Workspaces group.
# dnf group list
# dnf group install "KDE Plasma Workspaces"
I restarted the machine and I was presented with gdm. I selected KDE (obviously) and logged in. So far, so good.
Then I decided to change the gdm to sddm.
# dnf install sddm
# systemctl status gdm.service
# systemctl disable gdm.service
# systemctl enable sddm.service
After a reboot I could not login anymore. Neither my user password, nor root password worked.
I logged in on the second console (Ctrl+Alt+F2) as root and checked /var/log/messages. I found the following entries:
Sep 24 00:14:35 xxx kernel: audit: type=2300 audit(1443050075.602:649): pid=6160 uid=0 auid=500 ses
=4 subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='pam: default-context=unconfined_u:unconfined_r:unc
onfined_t:s0-s0:c0.c1023 selected-context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 exe="/
usr/libexec/sddm-helper" hostname=? addr=? terminal=:0 res=success'
Checking status of the sddm service also was returning some errors regarding PAM authentication problems and not being able to find the user.
I logged in on the second console as regular user , started X and changed the sddm settings from System Settings > Statup and Shutdown > Login Screen (SDDM). Rebooted the machine... and still the same problem and same errors.
I checked the /etc/sddm.conf only to find out that all the changes made in GUI were not saved there.
I manually then edited the file to look like this:
# cat /etc/sddm.conf
One of the main problems was that my user has the UID=500 and the default value for MinimumUid was 1000. Changing the value in GUI was not reflected in this config, so I changed it manually again.
After that I created a user's photo icon with the filename username.face.icon and format PNG image data, 62 x 63, 8-bit/color RGB, non-interlaced. I then copied it to /usr/share/sddm/faces/.
Finally, I restarted sddm service, logged out from the second console and restarted the laptop.
Now I was presented with my local user, selected Plasma and logged in without problem.
Maybe this will help you too. ;-)
I did not remove Gnome. Why not to switch from time to time and see what is going on there? The same like with different distros. There is no better or worse, there is only different taste. I like blueberries, you like pears. ;-)