Beleentoro Pro might be something for you. Basically a chill factory game, which I enjoyed for a long time. Other games by the developer Yiotro might be worth a look too.
There are also free versions of most of their games available, with ads iirc (not sure, has been a while). But if you don’t want the ads: the pro versions are really cheap. One time purchase for everything.

Another idea I have a puzzle game called: Mekorama by Martin Magni. The last time I played you got an option to pay what you think the game is worth at the end of the game. But you don’t have to.

Mini Metro by Dinosaur Polo Club is also really good, but comes with a purchase.

If you like tower defense, Bloons TD 5 by Ninja Kiwi is a must have. Comes with a purchase and has the option of microtransactions for cosmetics, but you can get those by playing as well. More importantly, it’s tons of fun.

In case you’ve got a Netflix subscription, check out their games. They have lots of games in their repertoire which you would have to buy if you went through the App/Play stores. (Bloons TD 5 should be included there for example.)