I will nominate Yu-gi-oh Duel Links, as well. Although the competitive meta continues to be in a weird place due to the low volume of cards in the game, if you’re just starting out it really is the best TCG experience you can have on mobile. There is very little pressure to use real money (I played consistently for about 4 months and never spent a dime).
This game completely captures the same fun of playing the full game. Trying to judge whether or not a person has a face down “Mirror Wall” is as stressful as ever. And with a with a ton of single-player content it’s not boring to play even if you don’t want to duel competitively. Konami also updates the game constantly, so it rarely gets stale. There are also really good tutorials/training areas that make it simple to learn the rules of the game, which is especially helpful for new players.
Among modern TCGs Yu-gi-oh has become known for its massive card pool (unlike in Magic every set is always usable) and absurdly complicated rules (I still don’t really understand pendulum summons), but this game removes most of the hard mechanics to create a system that feels fresh and (most importantly) fun. It makes Yu-gi-oh accessible in a way that the real TCG never can be (barring Konami doing something drastic to card limiting rules), and for that alone I think this game deserves recognition.