We study a minimal modified gravity scenario in the symmetric teleparallel (nonmetricity) formulation, focusing on an inverse nonmetricity term with $f(Q)=Q+M^4{Q}^{-1}$. The model does not introduce additional free parameters relative to the standard cosmological model $\mathrm{\Lambda }\mathrm{CDM}$, but modifies the late-time expansion and linear growth via an enhanced effective gravitational coupling. We identify key signatures: an enhanced matter power spectrum and cosmic microwave background (CMB) lensing, alongside a reduced late-time integrated Sachs-Wolfe effect and a shift in CMB peak positions. We confront the model with CMB data alone and in combination with baryon acoustic oscillations, redshift-space distortions, supernovae Ia, and DES large-scale structure data, considering both fixed minimal neutrino mass and varying $\mathrm{\Sigma }{m}_{\nu }$. We find that the model typically prefers higher $H_0$ than $\mathrm{\Lambda }\mathrm{CDM}$, alleviating the $H_0$ tension, while its boosted growth tends to increase clustering amplitudes unless offset by larger neutrino masses when $\mathrm{\Sigma }{m}_{\nu }$ is free. Overall, CMB-only data provide at most weak statistical support compared to $\mathrm{\Lambda }\mathrm{CDM}$, whereas late-time measurements impose tight restrictions that largely remove any improvement, positioning this model as a minimal yet strongly constrained alternative to dark energy.

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• Alternative gravity theories
• Cosmological parameters
• Dark energy