Let
$F$
be a non-archimedean local field of characteristic different from 2 and residual characteristic
$p$
. This paper concerns the
$\ell$
-modular representations of a connected reductive group
$G$
distinguished by a Galois involution, with
$\ell$
an odd prime different from
$p$
. We start by proving a general theorem allowing to lift supercuspidal
$\overline {\mathbf {F}}_{\ell }$
-representations of
$\operatorname {GL}_n(F)$
distinguished by an arbitrary closed subgroup
$H$
to a distinguished supercuspidal
$\overline {\mathbf {Q}}_{\ell }$
-representation. Given a quadratic field extension
$E/F$
and an irreducible
$\overline {\mathbf {F}}_{\ell }$
-representation
$\pi$
of
$\operatorname {GL}_n(E)$
, we verify the Jacquet conjecture in the modular setting that if the Langlands parameter
$\phi _\pi$
is irreducible and conjugate-selfdual, then
$\pi$
is either
$\operatorname {GL}_n(F)$
-distinguished or
$(\operatorname {GL}_{n}(F),\omega _{E/F})$
-distinguished (where
$\omega _{E/F}$
is the quadratic character of
$F^\times$
associated to the quadratic field extension
$E/F$
by the local class field theory), but not both, which extends one result of Sécherre to the case
$p=2$
. We give another application of our lifting theorem for supercuspidal representations distinguished by a unitary involution, extending one result of Zou to
$p=2$
. After that, we give a complete classification of the
$\operatorname {GL}_2(F)$
-distinguished representations of
$\operatorname {GL}_2(E)$
. Using this classification we discuss a modular version of the Prasad conjecture for
$\operatorname {PGL}_2$
. We show that the ‘classical’ Prasad conjecture fails in the modular setting. We propose a solution using non-nilpotent Weil–Deligne representations. Finally, we apply the restriction method of Anandavardhanan and Prasad to classify the
$\operatorname {SL}_2(F)$
-distinguished modular representations of
$\operatorname {SL}_2(E)$
.