  In 2015, Mantoulidis and Schoen constructed $3$-dimensional asymptotically
Euclidean manifolds with non-negative scalar curvature whose ADM mass can be
made arbitrarily close to the optimal value of the Riemannian Penrose
Inequality, while the intrinsic geometry of the outermost minimal surface can
be ``far away'' from being round. The resulting manifolds, called extensions,
are geometrically not ``close'' to a spatial Schwarzschild manifold. This
suggests instability of the Riemannian Penrose Inequality. Their construction
was later adapted to $n+1$ dimensions by Cabrera Pacheco and Miao. In recent
papers by Alaee, Cabrera Pacheco, and Cederbaum and by Cabrera Pacheco,
Cederbaum, and McCormick, a similar construction was performed for
asymptotically Euclidean electrically charged Riemannian manifolds and for
asymptotically hyperbolic Riemannian manifolds, respectively, obtaining
$3$-dimensional extensions.
  This paper combines and generalizes all the aforementioned results by
constructing suitable asymptotically hyperbolic or asymptotically Euclidean
extensions with electric charge in $n+1$ dimensions for $n\geq2$. We study in
detail the sub-extremality of these manifolds, consider the so far unstudied
case of extremality in extensions with electric charge and allow more general
conditions for the metric of our extensions.
  Besides suggesting instability of a naturally conjecturally generalized
Riemannian Penrose Inequality, the constructed extensions give insights into an
ad hoc generalized notion of Bartnik mass, similar to the Bartnik mass estimate
for minimal surfaces proven by Mantoulidis and Schoen via their extensions, and
unifying the Bartnik mass estimates in the various scenarios mentioned above.
