On a i586 system with cpu that does not support see2 when sddm in invoked all you get is a pale blank Mageia background and nothing else.
This is caused by something is the qt5 stack which is a BuildRequires of sddm.
This bug is dependent upon https://bugs.mageia.org/show_bug.cgi?id=19799
See also bug 19257 and bug 19258 for more on related issues.
this is the samee issue in fact.
Fixing one will fix this one.
*** This bug has been marked as a duplicate of bug 19258 ***