XMage has non-LLM-based built in AIs, just using regular old if-then logic. Getting them to play against each other with no human interaction is the first thing I built. https://www.youtube.com/watch?v=a1W5VmbpwmY is an example with two of those guys plus Sleepy and Potato no-op players - they do a fine job with straightforward decks.
You could also use LLMs, just passing a different `type` in the config file. But then you'd be spending real money for slower gameplay and probably-worse results.