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

Calculating dependencies ... done!
Dependency resolution took 1.76 s (backtrack: 0/20).

[ebuild  N     ] dev-libs/lzo-2.10:2::gentoo  USE="(split-usr) -examples -static-libs" 587 KiB
[ebuild  N     ] dev-libs/trio-1.17.1::gentoo  USE="-doc" 456 KiB
[ebuild  N     ] media-libs/jg-1.0.0-r1:1::gentoo  13 KiB
[ebuild  N     ] media-libs/jg-2.0.0:1::gentoo  15 KiB
[ebuild  N     ] media-libs/alsa-topology-conf-1.2.5.1-r1::gentoo  USE="-verify-sig" 12 KiB
[ebuild  N     ] media-libs/alsa-ucm-conf-1.2.16.1::gentoo  USE="-verify-sig" 83 KiB
[ebuild   R    ] sys-libs/zlib-1.3.2-r1:0/1::gentoo  USE="minizip* -static-libs -verify-sig" 1290 KiB
[ebuild  N     ] media-libs/flac-1.5.0:0/11-14::gentoo  USE="cxx -debug -ogg -static-libs" CPU_FLAGS_X86="avx avx2" 1054 KiB
[ebuild  N     ] media-libs/speexdsp-1.2.1::gentoo  CPU_FLAGS_X86="sse sse2" 901 KiB
[ebuild  N     ] virtual/minizip-1.3.1:0/1::gentoo  USE="-static-libs" 0 KiB
[ebuild  N     ] dev-libs/miniz-3.1.2:0/3.1.2::gentoo  284 KiB
[ebuild  N     ] media-libs/alsa-lib-1.2.16.1::gentoo  USE="python -debug -doc -verify-sig" PYTHON_SINGLE_TARGET="python3_14 -python3_12 -python3_13 (-python3_15)" 1104 KiB
[ebuild  N     ] x11-libs/libXScrnSaver-1.2.5::gentoo  USE="-doc" 266 KiB
[ebuild  N     ] media-libs/libepoxy-1.5.10-r3::gentoo  USE="X -test" 325 KiB
[ebuild  N     ] x11-libs/libXcursor-1.2.3::gentoo  USE="-doc" 286 KiB
[ebuild  N     ] x11-libs/libXtst-1.2.5::gentoo  USE="-doc" 285 KiB
[ebuild  N     ] media-libs/libsdl3-3.4.18::gentoo  USE="X alsa dbus opengl udev (-aqua) -bidi -doc -ibus -io-uring -jack -kms -oss -pipewire -pulseaudio -sndio -test -usb -vulkan -wayland" CPU_FLAGS_X86="avx avx2 avx512f mmx sse sse2 sse3 sse4_1 sse4_2" 15285 KiB
[ebuild  N     ] games-emulation/jgrf-2.0.1:1::gentoo  USE="-vulkan" 343 KiB
[ebuild  N     ] games-emulation/mednafen-jg-1.32.1.1-r1:1::gentoo  CPU_FLAGS_X86="avx" 4327 KiB

Total: 19 packages (18 new, 1 reinstall), Size of downloads: 26907 KiB

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

media-libs/jg:1

  (media-libs/jg-1.0.0-r1:1/1::gentoo, ebuild scheduled for merge) USE="" pulled in by
    <media-libs/jg-2.0.0 required by (games-emulation/mednafen-jg-1.32.1.1-r1:1/1::gentoo, ebuild scheduled for merge) USE="" CPU_FLAGS_X86="avx"
    ^              ^^^^^                                                                                                                                                                                                   

  (media-libs/jg-2.0.0:1/1::gentoo, ebuild scheduled for merge) USE="" pulled in by
    >=media-libs/jg-2.0.0 required by (games-emulation/jgrf-2.0.1:1/1::gentoo, ebuild scheduled for merge) USE="-vulkan"
    ^^              ^^^^^                                                                                                                                                                         


It may be possible to solve this problem by using package.mask to
prevent one of those packages from being selected. However, it is also
possible that conflicting dependencies exist such that they are
impossible to satisfy simultaneously.  If such a conflict exists in
the dependencies of two different packages, then those packages can
not be installed simultaneously.

For more information, see MASKED PACKAGES section in the emerge man
page or refer to the Gentoo Handbook.


The following USE changes are necessary to proceed:
 (see "package.use" in the portage(5) man page for more details)
# required by games-emulation/jgrf-2.0.1::gentoo
# required by games-emulation/mednafen-jg-1.32.1.1-r1::gentoo
# required by =games-emulation/mednafen-jg-1.32.1.1-r1 (argument)
>=media-libs/libsdl3-3.4.18 udev
# required by virtual/minizip-1.3.1::gentoo[-static-libs]
# required by games-emulation/mednafen-jg-1.32.1.1-r1::gentoo
# required by =games-emulation/mednafen-jg-1.32.1.1-r1 (argument)
>=sys-libs/zlib-1.3.2-r1 minizip

 * In order to avoid wasting time, backtracking has terminated early
 * due to the above autounmask change(s). The --autounmask-backtrack=y
 * option can be used to force further backtracking, but there is no
 * guarantee that it will produce a solution.