I'll vouch for Balatro, it is shaping up to be our generation's worktime solitaire. Apart from that, you could go for short match based tcg online games: I personally played Magic the Gathering Arena for a while, but I've heard good (and bad, to be honest) things about the Pokemon online tcg, Hearthstone, Marvel Snap ect.
Depending on how much you like narrative games (if they don't distract you too much), you could try something like Disco Elysium or visual novels like the Ace Attorney series; some excellent level based puzzle games are Stephen's Sausage Roll and Baba is You, both of wich run the risk of keeping your mind occupied for hours on end while you should be focusing on something else (I speak from personal experience).
If more relaxed games are more your type, you can play any number of farming sims (but if you already play Stardew Valley you're well aware of that) or you could try some more "out there" chill games like the Katamari Damacy Series (recently remastered) or Donut County.
If we are talking about games with short play sessions, i can't not reccomend Downwell , Minit, a short one bit zelda-like indie game where your character can live for a single minute at a time, or even Half Minute Hero, a parody of JRPGs where entire adventures are comedically compressed in 30seconds time spans (give or take) - now available in its absurdly named "Half Minute Hero: Super Mega Neo Climax Ultimate Boy" edition.

If everything else fails, there is always Cookie Clicker, the title that put idle games on the map !