Comment # 28 on bug 1176195 from Dominique Leuenberger

> I don't like that, first of all that is mostly was needed for X sessions and probably stay so historically. And why I need xdm when the goal to have X free DE, everything working through systemd natively instead of going through xdm script sounds better IMHO.

'liking' is no argument to break complete environments. We build a whole distro
with choice of DE for the user, going as far as co-existing environments on one
machine. Every DE / DM will have to adhere to this or they are not nice
citizens in the openSUSE eco system.

> I think I just skip "alternatives" and add systemd-preset to enable greetd if that would be accepted.

Only the systemd preset packages are allowed to install presets. No other
package is allowed to do so. All DMs register as an alternative choice that can
be selected (yast2 alternarives modules)