We devise a relaxed-inertial subgradient extragradient method for solving pseudomonotone equilibrium problems on Hadamard manifolds. The method uses a self-adaptive step size that does not depend on the Lipschitz constant. Under suitable conditions, we demonstrate that every sequence produced by the proposed algorithms converges to a solution of the equilibrium problem. We also prove linear convergence of the proposed method when the bifunction satisfies strong pseudomonotonicity and Lipschitz continuity. We then provide an application of our main result to variational inequality and optimization problems using the proposed algorithms. We conclude our paper with a numerical example to verify our convergence result. Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give... [797 chars]