  Analyses of $B$ meson decays to charmless hadronic final states are an
important part of the Belle II program. They are sensitive to effects from
non-standard model physics and provide experimentally precise constraints on
the weak interactions of quarks. We present recent Belle II results on
branching fractions and direct $CP$-violating asymmetries of the decays $B^0
\rightarrow K^+\pi^-$, $B^+ \rightarrow K^+\pi^0$, $B^+ \rightarrow K^0\pi^+$,
and $B^0 \rightarrow K^0\pi^0$, and use these to test the standard model
through an isospin-based sum rule. In addition, we measure the branching
fraction and direct $CP$ asymmetry of the decay $B^+ \rightarrow \pi^+\pi^0$
and the branching fraction of the decay $B^0 \rightarrow \pi^+\pi^-$, which
contribute towards the determination of the CKM angle $\phi_2$. The data are
collected with the Belle II detector from the SuperKEKB asymmetric-energy
$e^+e^-$ collider, consisting of $387 \times 10^6$ $\Upsilon(4S)\rightarrow
B\bar{B}$ events. We obtain $-0.03 \pm 0.13 \pm 0.04$ for the sum rule, in
agreement with the standard model expectation of zero and with a precision
comparable to the best existing determinations.
