I.L. coordinated the multiwavelength observations, carried out the evaluation and led the writing of the paper. H.Okay., A.P.M., L.P., P.-O.P., J.P., F. Tavecchio and R.W.R. contributed to the dialogue and elements of the paper. I.A., C.C., J.E. and I. Myserlis contributed the millimetre-radio polarization information. B.A.-G., I.A., A.V.B., M.B., G.B., V.C., M.G.-C., C.H., J.J., V. Kravtsov, E.L., I.L, Okay.N., S.S.S. and A.S. contributed the optical polarization information. G.V.P. contributed the infrared polarization information. A.P.M., G.M.M., R.M., L.P., M. Perri and S.P. contributed the Swift and NuSTAR information. L.D.G., N.D.L., I.D., S.R.E., H.L.M., R.M., M.N., N.O., A. Paggi and A.L.P. contributed the IXPE evaluation. The remaining authors are a part of the multiwavelength follow-up and IXPE groups whose vital contribution made the multiwavelength polarization observations attainable.