<p>We present mumax⁺, an extensible GPU-accelerated micromagnetic simulator with a Python user interface, to address the challenges posed by current magnetism research into systems with complex magnetic ordering and interfaces. It is a general solver for the space- and time-dependent evolution of the magnetization and related vector quantities, using finite difference discretization. Here, we present its design and application and discuss features not available in mumax³, such as the modeling of antiferromagnets with magnetoelastic coupling. As an illustration of its capabilities, we use mumax⁺ to simulate state-of-the-art magnetic systems. Specifically, we demonstrate the current-induced domain wall motion in a polycrystalline antiferromagnet, we simulate the working principle of a strain-driven antiferromagnetic racetrack memory and we reproduce experimentally observed domain structures in a non-collinear antiferromagnet.</p>