Marginalized posterior distribution of the linear EFT model background parameter, Ω, with Ω parameterized as a linear function of the scale factor, i.e., Ω(a) = α_M0a, see Sect. 5.2.1. The equation of state parameter w_de is fixed to −1, and therefore, Ω₀ = 0 will correspond to the ΛCDM model. Here Planck means Planck TT+lowP. Adding CMB lensing to the data sets does not change the results significantly; high-ℓ polarization tightens the constraints by a few percent, as shown in Table 5.