AdS${}_3\times$ S${}^2$ in IIB with small $\mathcal{N}=(4,0)$ supersymmetry

We consider warped AdS${}_3\times$S${}^2\times$M${}_5$ backgrounds in type II supergravity preserving small $\mathcal{N}=(4,0)$ supersymmetry. We show that imposing $\mathcal{N}=(4,0)$ supersymmetry imposes between 0 and 3 a priori isometries in the internal M${}_5$. In this work we focus on classes of solution where M${}_5$ exhibits no a prioi isometry which imposes additional constraints. Solving these in IIA forces M${}_5$ to support an SU(2)-structure, a case already studied in arXiv:1908.09851, while in IIB one arrives at two broad new classes with identity structure that we reduce to local expressions for the physical fields and PDEs.