These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 0.98 s (backtrack: 0/20).


The following USE changes are necessary to proceed:
 (see "package.use" in the portage(5) man page for more details)
# required by gnome-extra/gnome-boxes-50.0::gentoo
# required by =gnome-extra/gnome-boxes-50.0 (argument)
>=dev-libs/libportal-0.9.1 gtk
# required by gnome-extra/gnome-boxes-50.0::gentoo
# required by =gnome-extra/gnome-boxes-50.0 (argument)
>=net-misc/spice-gtk-0.42-r4 smartcard usbredir
# required by gnome-extra/gnome-boxes-50.0::gentoo
# required by =gnome-extra/gnome-boxes-50.0 (argument)
>=app-emulation/spice-0.16.0 smartcard
# required by gnome-extra/gnome-boxes-50.0::gentoo
# required by =gnome-extra/gnome-boxes-50.0 (argument)
>=app-emulation/qemu-10.2.3-r2 usbredir smartcard spice
# required by gnome-extra/gnome-boxes-50.0::gentoo
# required by =gnome-extra/gnome-boxes-50.0 (argument)
>=sys-libs/libosinfo-1.12.0-r1 vala

!!! The ebuild selected to satisfy "sys-libs/libosinfo[vala]" has unmet requirements.
- sys-libs/libosinfo-1.12.0-r1::gentoo USE="-gtk-doc -introspection -test -vala"

  The following REQUIRED_USE flag constraints are unsatisfied:
    vala? ( introspection )

(dependency required by "gnome-extra/gnome-boxes-50.0::gentoo" [ebuild])
(dependency required by "=gnome-extra/gnome-boxes-50.0" [argument])