The Savage Worlds roleplaying system smashed together with the Rifts Megaverse setting (a post-post-apocalypse kicked off by the cataclysmic return of magic on Earth and the opening of inter-dimensional portals all over it) seems like a match made in multi-planar heaven.

The Foundry VTT support for this seems like it’s really good which would make running this crunchier system feasible for me.