It might not be the highlight in the Total War calendar, but from March 24, Total War Battles: Kingdom will invite you to engage in light cross-platform strategy on Steam and the usual mobile platforms.
Total War Battles: Shogun came to PC after it arrived on mobile and proved itself a competent strategy game, if a long way removed from the comprehensive empire-building of Total War proper. That was £3, and still required purchase of xp packs to make decent progress. Kingdom will be free, so you can bet that in-app purchases will abound.
It does look closer to Total War than its predecessor, however. The hex-based city-building is still there, but battles are rendered in rather more fulsome 3D than the units of Shogun.
The world persists between Steam and mobile, so if you're after something light for the commute Kingdom could suit.