Electronic Journal of Differential Equations, Vol. 2025 (2025), No. 66, pp. 1-15. Title: Solutions to nonlinear elliptic problems with nonhomogeneous operators and mixed nonlocal boundary conditions Authors: Eun Kyoung Lee (Pusan National Univ, Busan, Korea) Inbo Sim (Univ. of Ulsan, Korea) Byungjae Son (Ohio Northern Univ., OH, USA) Abstract: We investigate the existence, multiplicity and nonexistence of positive solutions to nonlinear (singular) elliptic problems involving nonhomogeneous operators and mixed nonlocal boundary conditions based on the behaviors of the nonlinear term near $0$ and $\infty$. In particular, we discuss the existence of at least three positive solutions to the mixed nonlocal boundary problems, which is new finding even for the problems involving homogeneous operators. The novelty of this study lies in constructing completely continuous operators related to nonlinear elliptic problems involving complicated boundary conditions. We emphasize that only one fixed point theorem is used to obtain the existence and multiplicity results, despite generalizing and extending most of the problems in previous literature. Submitted February 20, 2025. Published June 30, 2025. Math Subject Classifications: 34B10, 34B16, 34B18. Key Words: Singular elliptic problem; nonhomogeneous operator; integral boundary condition; multipoint boundary condition; positive solution.