[ebuild     U ] gnome-base/gnome-shell-40.1-r1 [3.38.3] USE="browser-extension ibus networkmanager systemd -bluetooth (-elogind) -gtk-doc -telepathy -test" PYTHON_SINGLE_TARGET="python3_9* -python3_8 (-python3_7%*)" 

!!! Multiple package instances within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict:

gnome-base/gnome-shell:0

  (gnome-base/gnome-shell-40.1-r1:0/0::gentoo, ebuild scheduled for merge) USE="browser-extension ibus networkmanager systemd -bluetooth (-elogind) -gtk-doc -telepathy -test" ABI_X86="(64)" PYTHON_SINGLE_TARGET="python3_9 -python3_8" pulled in by
    =gnome-base/gnome-shell-40.1-r1 (Argument)

  (gnome-base/gnome-shell-3.38.3:0/0::gentoo, installed) USE="browser-extension ibus networkmanager systemd -bluetooth (-elogind) -gtk-doc -telepathy -test" ABI_X86="(64)" PYTHON_SINGLE_TARGET="python3_7 -python3_8 -python3_9" pulled in by
    =gnome-base/gnome-shell-3.38* required by (gnome-extra/gnome-shell-extensions-3.38.2:0/0::gentoo, installed) USE="" ABI_X86="(64)"
    ^                       ^^^^^