The new mesa-24.1.0 package drops USE flags gles2 and egl, which are required by a couple of gstreamer based packages like media-libs/gst-plugins-base-1.22.11, media-plugins/gst-plugins-vaapi-1.22.11.
I have got the same issue WARNING: One or more updates/rebuilds have been skipped due to a dependency conflict: media-libs/mesa:0 (media-libs/mesa-24.1.0:0/0::gentoo, ebuild scheduled for merge) USE="X llvm lm-sensors (opengl) proprietary-codecs vdpau vulkan wayland xa zstd -d3d9 -debug -opencl -osmesa (-selinux) -test -unwind -vaapi -valgrind -vulkan-overlay (-zink)" ABI_X86="32 (64) (-x32)" CPU_FLAGS_X86="sse2" LLVM_SLOT="17 -15 -16" VIDEO_CARDS="vmware -d3d12 (-freedreno) -intel -lavapipe (-lima) -nouveau (-nvk) (-panfrost) -r300 -r600 -radeon -radeonsi (-v3d) (-vc4) -virgl (-vivante)" conflicts with media-libs/mesa[gles2,egl(+),X,abi_x86_32(-),abi_x86_64(-)] required by (media-plugins/gst-plugins-vaapi-1.22.11:1.0/1.0::gentoo, installed) USE="X drm egl gles2 nls opengl wayland -test" ABI_X86="32 (64) (-x32)" ^^^^^ >=media-libs/mesa-9.0[egl(+),gbm(+),gles2,wayland,abi_x86_32(-),abi_x86_64(-)] required by (media-libs/gst-plugins-base-1.22.11:1.0/1.0::gentoo, installed) USE="X alsa egl gbm gles2 introspection nls ogg opengl orc pango theora vorbis wayland -ivorbis -test" ABI_X86="32 (64) (-x32)" ^^^^^
*** This bug has been marked as a duplicate of bug 932515 ***
