Mine so far is wingspan, my dads been bugging me to download Root.
Star Realms is pretty good for a quick few rounds during downtime.
Or the fantasy themed version Hero Realms! I slightly prefer this one, but both are great and you can try them for free.
Ascension is my most played by far. It’s one of the earliest deckbuilders and the first one (I think) with the river-style market which has been used in many other deckbuilders since. The developers have done a great job exploring various mechanisms in the expansions over the years and most of the content is available in the digital version too. My favorite sets are the ones that use Insight (the amber gems): Dreamscape, Delirium, Deliverance.
Besides the game mechanics the great art, music and the smooth app make it very chill and enjoyable for me.
On recommendation from /r/soloboardgaming, I like both One Deck Dungeon and Through The Ages.
The Dominion app. That shit made me learn strategies really quickly
The Dominion app is great. It is also cross buy with the Dominion PC version on Steam, and the price on the Android store is usually a bit lower.
I really like Deep Space D6 for Android (it might be on IOS too). It’s a quick and easy game, that I like playing on the phone when there’s nothing else to do. The game is very basic without cool graphics, but that’s what I like about it.