LAPACK is explicitly threaded now, at least in the better implementations. MKL threads at the LAPACK level, not just with BLAS calls, since that’s not efficient. Even reference LAPACK has some threading now, e.g. lapack/zhetrd_hb2st.F at 2614d23900915235f9652a5a2ad3e1873e7ac9f0 · Reference-LAPACK/lapack · GitHub, and even using OpenMP tasking (lapack/dsytrd_sb2st.F at 2614d23900915235f9652a5a2ad3e1873e7ac9f0 · Reference-LAPACK/lapack · GitHub).