I’ve put a disgusting amount of hours into Emberward. It’s Tower Defense but no mtx and has a really fun Tetris blocks gimmck to build lanes.

https://store.steampowered.com/app/2459550/Emberward/

Yes it’s early access but it doesn’t matter, the game is nearly done anyways, also on sale currently. There’s good Steam Input profiles for the Deck. Dev is adding controller suppport for 1.0 but this doesn’t really matter on a Steam Deck.