  Localized or propagating Majorana boundary modes are the key feature of
topological superconductors. They are rare in naturally-occurring compounds,
but the tailored manipulation of quantum matter offers opportunities for their
realization. Specifically, lattices of Yu-Shiba-Rusinov bound states $-$ Shiba
lattices $-$ that arise when magnetic adatoms are placed on the surface of a
conventional superconductor can be used to create topological bands within the
superconducting gap of the substrate. Here, using scanning tunnelling
microscopy to create and probe adatom lattices with single atom precision we
reveal two signatures consistent with the realization of two types of mirror
symmetry protected topological superconductors. The first has edge modes as
well as higher-order corner states, and the second has symmetry-protected bulk
nodal points. In principle, their topological character and boundary modes
should be protected by the spatial symmetries of the adatom lattice. Our
results highlight the potential of Shiba lattices as a platform to design the
topology and sample geometry of 2D superconductors.
