/usr/include/mono-2.0/ is in libmono-2.0-dev 3.2.8+dfsg-10.
This file is owned by root:root, with mode 0o755.
..
/usr/include/mono-2.0/mono/
/usr/include/mono-2.0/mono/cil/
/usr/include/mono-2.0/mono/cil/opcode.def
/usr/include/mono-2.0/mono/jit/
/usr/include/mono-2.0/mono/jit/jit.h
/usr/include/mono-2.0/mono/metadata/
/usr/include/mono-2.0/mono/metadata/appdomain.h
/usr/include/mono-2.0/mono/metadata/assembly.h
/usr/include/mono-2.0/mono/metadata/attrdefs.h
/usr/include/mono-2.0/mono/metadata/blob.h
/usr/include/mono-2.0/mono/metadata/class.h
/usr/include/mono-2.0/mono/metadata/debug-helpers.h
/usr/include/mono-2.0/mono/metadata/debug-mono-symfile.h
/usr/include/mono-2.0/mono/metadata/environment.h
/usr/include/mono-2.0/mono/metadata/exception.h
/usr/include/mono-2.0/mono/metadata/image.h
/usr/include/mono-2.0/mono/metadata/loader.h
/usr/include/mono-2.0/mono/metadata/metadata.h
/usr/include/mono-2.0/mono/metadata/mono-config.h
/usr/include/mono-2.0/mono/metadata/mono-debug.h
/usr/include/mono-2.0/mono/metadata/mono-gc.h
/usr/include/mono-2.0/mono/metadata/object.h
/usr/include/mono-2.0/mono/metadata/opcodes.h
/usr/include/mono-2.0/mono/metadata/profiler.h
/usr/include/mono-2.0/mono/metadata/reflection.h
/usr/include/mono-2.0/mono/metadata/row-indexes.h
/usr/include/mono-2.0/mono/metadata/sgen-bridge.h
/usr/include/mono-2.0/mono/metadata/threads.h
/usr/include/mono-2.0/mono/metadata/tokentype.h
/usr/include/mono-2.0/mono/metadata/verify.h
/usr/include/mono-2.0/mono/utils/
/usr/include/mono-2.0/mono/utils/mono-dl-fallback.h
/usr/include/mono-2.0/mono/utils/mono-error.h
/usr/include/mono-2.0/mono/utils/mono-logger.h
/usr/include/mono-2.0/mono/utils/mono-publib.h