Abstract: 6D Little String Theories (LSTs) are an interesting class of UV complete theories which possess both QFT-like properties, such as higher-form global symmetries, and gravity-like properties, such as T-duality. In particular, this talk will focus on Heterotic LSTs and explore the T-duality landscape of such theories when discrete symmetry twists are allowed along the compactification circle. Starting from charge conjugation twists, we construct duality chains with (un)twisted LSTs by utilizing the duality invariant data and carefully considering the massive spectrum. This significantly extends the known T-duality landscape. To fully prove the duality, we realize dual theories as arising from inequivalent fibrations in F-theory on the same non-compact genus-one fibered Calabi-Yau (CY) manifold, and then use M/F-theory duality. Furthermore, we also consider discrete symmetries corresponding to the permutation of tensor multiplets and — based on the invariant data — construct a new class of duals (CHL-like twisted LSTs) with no known geometric construction.