Marginalized posterior of log|f_R0| using observations of Planck modeled with MGCLASS. TTTEEE refers to the temperature and polarization power spectra of Planck, “lensing” to the addition of the CMB lensing power spectrum, and A_lens to the inclusion of the lensing amplitude. “A_lens in TTTEEE only” means that the effect of A_lens on the observed CMB lensing convergence power spectrum is not taken into account; only the CMB temperature and polarization power spectra are affected by A_lens (see the text for details).