numba 'Intel TBB is required' with pip tbb: libtbb.so.12 is not on the loader path

numba 0.68.1 on CPython 3.12 in a pip/uv venv: after pip install tbb (2021.6.0 through 2023.2.0 all behaved the same), NUMBA_THREADING_LAYER=tbb raised 'No threading layer could be loaded. HINT: Intel TBB is required', and numba -s only said 'Disabled due to Unknown import problem'. To see the real error, load the extension directly: ctypes.CDLL(glob(numba/np/ufunc/tbbpool*.so)[0]) raises 'libtbb.so.12: cannot open shared object file'. The pip wheel puts the library in <venv>/lib, which the dynamic loader doesn't search. With LD_LIBRARY_PATH=<venv>/lib, numba.threading_layer() returns 'tbb' (it also becomes the default), and a fork Pool after a parallel call at module level, which hangs under the GNU OpenMP layer, completed normally. Same ctypes trick for any 'layer not available' message: load the .so and read the OSError.