emerge -auDN @world

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

Calculating dependencies \

!!! Problem resolving dependencies for media-gfx/blender from @selected
... done!

!!! The ebuild selected to satisfy "media-gfx/blender" has unmet requirements.

• media-gfx/blender-2.93.2::media-kit USE="bullet color-management cycles dds ffmpeg fftw fluid gmp jpeg2k nls oidn openexr openimageio openmp opensubdiv openvdb osl pdf potrace pugixml sdl sndfile system-numpy system-python tbb tiff -alembic -collada -cuda -debug -doc -embree -headless -jack -jemalloc -man -ndof -openal -opencl -pulseaudio -standalone -valgrind" PYTHON_SINGLE_TARGET="-python3_9" PYTHON_TARGETS="-python3_9"

The following REQUIRED_USE flag constraints are unsatisfied:
python_single_target_python3_9

The above constraints are a subset of the following complete expression:
exactly-one-of ( python_single_target_python3_9 ) alembic? ( openexr ) cuda? ( cycles ) cycles? ( openexr tiff openimageio ) fluid? ( tbb ) opencl? ( cycles ) openvdb? ( tbb ) osl? ( cycles ) standalone? ( cycles )

(dependency required by "@selected" [set])
(dependency required by "@world" [argument])