We review recent progress in the study of S-folds in light of the gauge/gravity duality and the AdS swampland conjecture. S-folds correspond to non-geometric backgrounds of type IIB supergravity of the form AdS_4 × S^1 × M that involve a non-trivial SL(2, Z) (S-duality) monodromy for the type IIB fields when moving around the S^1. We present four such solutions with M = S^5 that preserve N = 4, 2, 1, 0 supersymmetries. Via the AdS/CFT correspondence, these solutions are conjectured to describe new strongly coupled three-dimensional CFT's on a localised interface of SYM. We discuss the existence of flat deformations in the gravity side dual to marginal deformations of the conjectured S-fold CFT’s. From a geometrical perspective, the flat deformations induce a monodromy h on M and replace S^1 × M by the so-called mapping torus T(M)_h. Interestingly, the flat deformations provide a controlled mechanism of supersymmetry breaking for N ≥ 2 S-folds. We present a class of such non-supersymmetric S-folds obtained by flat-deforming the N = 4 S-fold and discuss their (non-)perturbative stability.