• I love all the Buttonshy wallet games: Sprawlopolis, Rove, and Food Chain Island in particular are great.
• Maybe a bit on the heavier side, but I currently really enjoy Imperium: Classics/Imperium: Legends. They have a great solo mode and really scratch that deck building itch.

There's also Five Parsecs from Home, which is a solo wargame / RPG. You only need a handful of minis, and it's miniature-agnostic so that you can use any mini you want.