  We show that certain amenable subgroups inside $\tilde{A}_2$-groups are
singular in the sense of Boutonnet and Carderi. This gives a new family of
examples of singular group von Neumann subalgebras. We also give a geometric
proof that if $G$ is an acylindrically hyperbolic group, $H$ is an infinite
amenable subgroup containing a loxodromic element, then $H<G$ is singular.
Finally, we present (counter)examples to show both situations happen concerning
maximal amenability of $LH$ inside $LG$ if $H$ does not contain loxodromic
elements.
