/usr/lib/x86_64-linux-gnu/libSDL2.so is in libsdl2-dev 2.0.2+dfsg1-3ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libSDL2-2.0.so.0.2.0
/usr/lib/x86_64-linux-gnu/libSDL2-2.0.so.0.2.0