Dynamics of linear scalar perturbation in f(Q)+f(T) class of f(Q,T) gravity

In this work, we study the [Formula: see text] model of symmetric teleparallel modified gravity in the framework of cosmological perturbation theory. Using a general approach, we extract the differential matter density equation then we simplify it as a second-order equation by considering the sub-Hubble approximation. Our analysis is then based on two different forms of [Formula: see text] that we study in a classic approach and again using Holographic dark energy. Our initial results yield a significant divergence from the perturbed behavior of the [Formula: see text] CDM model, imposing stringent constraints on the feasibility of this class of theories but the HDE contribution triggers an interesting discussion.