I think Balatro uses the Love2d engine which is in C/C++.

Sure, but you write games in it in Lua. That Love2d is implemented in C++ (GitHub says like 80% C++ and 10% C) doesn't mean that you're writing the game in it. In my understanding, Love2d uses reference counting (which is still GC) for its own stuff, and integrates those into Lua's tracing GC.