Depends what you mean by newish and iPhone XS compatible. Warbits was last updated 2 years ago and it’s not full screen on the X. But it’s probably the closest thing to AW you will find on iOS.
Yeah, I'll second Warbits, and add Lost Frontier. It's not new.... and I have no idea if it's been updated for the newer screen sizes, but it's another great take on the AW formula. Another one is Uniwar. It's.... OLD (in AppStore years.... I think it came out back around 2010 or 2011). Other than that.... everything I've played that was supposed to be influenced by Advance Wars got deleted from my phone VERY quickly or disappeared during the 64bit overhaul.