BSM scenarios with missing energy at future lepton colliders

I will briefly discuss the signatures and discovery prospects of several new physics models containing dark matter candidates at future lepton colliders. In particular, I will discuss the two models that, among other signatures, lead to electroweak gauge bosons and missing energy: the Inert Doublet Model, as well as the THDMa, a two Higgs doublet model with an additional pseudoscalar that serves as a portal to the dark sector. Results are mainly based on a Snowmass Whitepaper arXiv:2203.07913