  Searches for new phenomena inspired by supersymmetry in final states
containing an $e^+e^-$ or $\mu^+\mu^-$ pair, jets, and missing transverse
momentum are presented. These searches make use of proton-proton collision data
with an integrated luminosity of 139 $\text{fb}^{-1}$, collected during
2015-2018 at a centre-of-mass energy $\sqrt{s}=13 $TeV by the ATLAS detector at
the Large Hadron Collider. Two searches target the pair production of charginos
and neutralinos. One uses the recursive-jigsaw reconstruction technique to
follow up on excesses observed in 36.1 $\text{fb}^{-1}$ of data, and the other
uses conventional event variables. The third search targets pair production of
coloured supersymmetric particles (squarks or gluinos) decaying through the
next-to-lightest neutralino $(\tilde\chi_2^0)$ via a slepton $(\tilde\ell)$ or
$Z$ boson into $\ell^+\ell^-\tilde\chi_1^0$, resulting in a kinematic endpoint
or peak in the dilepton invariant mass spectrum. The data are found to be
consistent with the Standard Model expectations. Results are interpreted using
simplified models and exclude masses up to 900 GeV for electroweakinos, 1550
GeV for squarks, and 2250 GeV for gluinos.
