IIRC it's "solved" for heads up but not really multiway like 3+ to the flop. I believe in a recent Bart Hanson Youtube he points out that mutltiway is not solved.
> Machines have raised the stakes once again. A superhuman poker-playing bot called Pluribus has beaten top human professionals at six-player no-limit Texas hold’em poker, the most popular variant of the game. It is the first time that an artificial-intelligence (AI) program has beaten elite human players at a game with more than two players
It's not solved for multiway in the sense that the optimal move in each situation isn't known, but there are AIs like Pluribus that have superhuman performance.
Those constraints don't seem that strong to me. The algorithm could've just been retrained with different stack sizes if it ended up making a big enough difference.
> Machines have raised the stakes once again. A superhuman poker-playing bot called Pluribus has beaten top human professionals at six-player no-limit Texas hold’em poker, the most popular variant of the game. It is the first time that an artificial-intelligence (AI) program has beaten elite human players at a game with more than two players
https://www.nature.com/articles/d41586-019-02156-9#ref-CR1