Positive Solutions for a Semipositone Singular ψ–Riemann–Liouville Fractional Boundary Value Problem

We explore the existence of positive solutions to a ψ–Riemann–Liouville fractional differential equation with a parameter and a sign-changing singular nonlinearity, supplemented with nonlocal boundary conditions which contain Riemann–Stieltjes integrals and various fractional derivatives. To establish our main results, we use the Guo–Krasnosel’skii fixed-point theorem.