Smash Run was a pretty nice feature to the 3DS Version of Smash 4, where you'd fight your way through a large open area tackling familiar enemies from the playable franchises represented in the game. Unfortunately Ultimate lacks a mode that has you playing in open spaces, which was also had in Melee's Adventure Mode and Brawl's Subspace Emissary, with all gameplay taking place entirely on stages. If Ultimate can have Stage Builder return in a future update (along with potentially Homerun Contest as well at a later date), then other modes from previous games like Smash Run could appear as well. One thing they should certainly implement into Smash Run if it appears in Ultimate in some form is having Co-Op Gameplay (which I hear was even an abandoned feature from the 3DS Version of Smash 4).