/usr/ is in libsdl2-mixer-dev 2.0.2+dfsg1-2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/
/usr/lib/x86_64-linux-gnu/
/usr/include/
/usr/include/SDL2/
/usr/include/SDL2/SDL_mixer.h
/usr/lib/x86_64-linux-gnu/libSDL2_mixer.a
/usr/lib/x86_64-linux-gnu/pkgconfig/
/usr/lib/x86_64-linux-gnu/pkgconfig/SDL2_mixer.pc
/usr/share/
/usr/share/doc/
/usr/share/doc/libsdl2-mixer-dev/
/usr/share/doc/libsdl2-mixer-dev/copyright
/usr/share/doc/libsdl2-mixer-dev/examples/
/usr/share/doc/libsdl2-mixer-dev/examples/Makefile
/usr/share/doc/libsdl2-mixer-dev/examples/playmus.c
/usr/share/doc/libsdl2-mixer-dev/examples/playwave.c
/usr/lib/x86_64-linux-gnu/libSDL2_mixer-2.0.so
/usr/lib/x86_64-linux-gnu/libSDL2_mixer.so
/usr/share/doc/libsdl2-mixer-dev/changelog.Debian.gz