  We consider superconductor-normal-superconductor-normal-superconductor
(SNSNS) planar Josephson junctions in hole systems with spin-orbit interaction
that is cubic in momentum (CSOI). Using only the superconducting phase
difference, we find parameter regimes where junctions of experimentally
achievable transparency can enter a topological superconducting phase with
Majorana bound states (MBSs) at the junction ends. In planar germanium
heterostructures CSOI can be the dominant form of SOI and extremely strong. We
show analytically and numerically that, within experimental regimes, our
results provide an achievable roadmap for a new MBS platform with low disorder,
minimal magnetic fields, and very strong spin-orbit interaction, overcoming
many of the key deficiencies that have so far prevented the conclusive
observation of MBSs.
