emerge -uDp world returns a message saying: !!! Multiple package instances within a single package slot have been pulled !!! into the dependency graph, resulting in a slot conflict: dev-qt/qtgui:5 (dev-qt/qtgui-5.15.8-r1:5/5.15.8::gentoo, ebuild scheduled for merge) USE="X dbus egl jpeg libinput png udev wayland -accessibility -debug -eglfs -evdev -gles2-only -ibus -linuxfb -test -tslib -tuio -vnc -vulkan" ABI_X86="(64)" pulled in by =dev-qt/qtgui-5.15.8*[-gles2-only] required by (dev-qt/qtwayland-5.15.8:5/5.15.8::gentoo, ebuild scheduled for merge) USE="X -debug -test -vulkan" ABI_X86="(64)" ^ ^^^^^^^ (and 10 more with the same problem) (dev-qt/qtgui-5.15.7:5/5.15.7::gentoo, installed) USE="X dbus egl jpeg libinput png udev wayland -accessibility -debug -eglfs -evdev -gles2-only -ibus -linuxfb -test -tslib -tuio -vnc -vulkan" ABI_X86="(64)" pulled in by =dev-qt/qtgui-5.15.7*:5/5.15.7=[dbus] required by (dev-qt/qtwidgets-5.15.7:5/5.15::gentoo, installed) USE="X dbus gtk png -debug -gles2-only -test" ABI_X86="(64)" ^ ^^^^^^^^^^^^^^^^^ dev-qt/qtgui:5/5.15.7= required by (media-video/smplayer-22.2.0:0/0::gentoo, installed) USE="-autoshutdown -bidi -debug -mpris" ABI_X86="(64)" ^^^^^^^^^^ (and 8 more with the same problems) ... Most likely, media-video/smplayer-22.2.0, marked as stable at the time of filling this bug report, needs a version bump to 22.7.0.
Seek help in IRC or Gentoo Forums with your slot conflict, it is wholly unrelated to smplayer.
*** This bug has been marked as a duplicate of bug 893952 ***