Single column of the low-resolution 30 (top section), 44 (middle section), and 70 GHz (bottom section) frequency channel covariance matrix, as estimated analytically by the LFI DPC (top rows) and by posterior sampling in BEYONDPLANCK (bottom rows). The selected column corresponds to the Stokes Q pixel marked in gray, which is located in the top right quadrant in the BEYONDPLANCK maps. Note that the DPC covariance matrix is constructed at N_side = 16 and includes a cosine apodization filter, while the BEYONDPLANCK covariance matrix is constructed at N_side = 8 with no additional filter. The temperature components are smoothed to 20° FWHM in both cases, and Planck 2018 additionally sets the TQ and TU elements by hand to zero for the 70 GHz channel.