Trend of the tensor-to-scalar ratio r_fgds fitted on the NILC foregrounds residuals angular power spectra with the likelihood of Eq. (26) when the sky fraction of the employed mask varies. The adopted masking strategy is the second one described in Sect. 4.1: we mask the most contaminated regions by foregrounds residuals. In this case, the input multi-frequency B-mode maps are constructed full-sky and then masked. The considered cases are SWIPE+Planck (left) with both d0s0 (red) and d1s1 (green) Galactic models and SO-SAT dataset (right) assuming only the d1s1 sky model. The grey shaded areas show the targeted sensitivity of the LSPE and SO experiments. The angular power spectra in the likelihood are binned with Δℓ = 15. The error bars indicate the bounds at 2σ (left) and 1σ (right) obtained from the posterior distributions.