If you’re talking about two-player perfect information games (https://en.wikipedia.org/wiki/Perfect_information) with players alternatingly choosing between finitely many moves known at the start of the game, I don’t think any game would hold up long today against attempts to write a world-champion crushing program.
That’s likely limiting the set of games a lot more than needed, but I want to rule out games such as Nomic (https://en.wikipedia.org/wiki/Nomic), where I think humans still have an edge. Chances are you’re not calling that “an alternative to chess”, though, as it’s quite different from it.
- Party games (e.g. Apples to Apples, Jackbox)
- Complex video games like FPSs (with enough mechanics and graphics that aimbots would have difficulty), Trackmania, Elden Ring. They have to be real-time competitions otherwise you can just use TAS
- Simon says